I only have a minute to post and I'll write as fast as I can! We moved from NoVa to Seattle a couple months ago, and with only what fit in our Rav-4. I had my guitar shipped out by a friend, since it wouldn't fit. :^/ But we left most everything behind, and only brought the most important clothes, documents, pots and pans (All-Clad, how could I leave them?! :^p), a few toys (including heavy train stuff, legos, a bag of soft snuggle buddies, a bag of books), my sewing machine, our sleeping bag and blanket and pillows.. and that's all I can think of at the moment. There was more that I can't think of and we packed the back full, even though we never meant to or thought we actually would. That turned out to be an annoyance, for obvious reasons. We could've hitched a trailer; we've got the set up for it, but we didn't want to "risk it", so to speak, because we've just never done that before and it seemed too dangerous (and considering the insane storms we went through in Wy and Montana, it was probably extremely wise! (But only in hindsight. ;^p))
One important thing: Things can always be obtained again, somehow, someway, even for free. We would've brought even less if we had known how freaking expensive the gas would be- Because we had the back loaded. It was heavy. We just took a trip down to the Oregon coast, and didn't even have to stop for gas. On the way from Va to Seatown, every time we stopped, dh got coffee and gas. We didn't realize how much gas mileage was actually lost (plus money) on that trip until we went to Oregon last weekend. The difference was quite insane, let me tell you.
We planned on buying beds and a couch or something to sit on, but just bought beds, and were lucky enough to get a couch and table and chairs for free from friends. This is the first time I've ever had an actual dining table and chairs in my life, ha! Still, they're only used for dh to lay his hoodie on when he comes home from work. Anyway, we bought beds, and I would suggest getting a cheap futon for your family once you get to where you will be. Our dd is 5 1/2 now and is so big, and she still squeezes in with us on occasion (last night :^p), but our queen bed we have now doesn't fit us all well, and she has her own full bed now. She slept with us all the time up until a month ago or so. She just doesn't fit anymore! :^p So, considering your dd is so young, my opinion is that you guys will be just fine with a full or queen cheap bed of whatever sort for a long time. Even two small futons, since you'll have two little ones soon (two futons for you all to sleep on). Before that though, you could do with an air mattress for a few months, and that's all I can think of regarding that. We've used them after moving for a few months a couple times, and they're just fine for that amount of time. There are also sleeping bags/pads to use, which is what I'd do in your situation. Just wanted to throw out the air mattress idea out there, too; slightly more comfy, I guess.
Honestly, you really only need to bring what you -really, really- need, and nothing more. The gas expense + possible-trailer expense would be crazy. And I mean Crazy. We learned that the hard way, and we just had a small SUV of stuff. Dishes, clothes, furniture of any sort- they can be purchased again, and for cheap or free. You never know what will happen, and we were very pleasantly surprised, and had no idea the furniture situation would work out so well for us. And we moved from a 1100 apt to a 864 or something..? We were in 2 bd 2 bth before and now 2 bd 1 bth, and it's fantastic. And I am a serious minimalist, and really thought I was before we moved. And the cupboards didn't have much in them, and we didn't have much furniture, and I was SHOCKED, shocked, I say! At how very much stuff there actually turned out to be when it was all out and we were getting a pile in a corner of the living room of what we were going to take. I still can't believe how much stuff there was, because of what I thought there actually was, if you see what I'm saying. So I lived my dream of leaving most everything and moving across the country in our truck, and it was wonderful. But now I know that I really didn't have to bring a whole bin of clothes of mine and dd's, and all those toys. They could've all been bought again. Even the pots and pans; they were so heavy. They were expensive and I used them often, but we could've made the trip easier and bought thing again cheaper once here, and I could've gotten new great pots and pans if I really needed them for Christmas or something. In hindsight I could've made that trip much, much better and easier than I thought I was at the time!
I wish I could have my dh write some of this to give his ideas too, and so maybe your dh could read and get ideas or whatever, but those are my thoughts (and I told dh what I was writing about and he said not to forget the weight of the truck, gas mileage and gas costs! ;^p). If you have any questions I would love to answer them. I hope I got my ideas across okay; I'm not the most articulate person in the world... My main point I think I'm trying to make is that I would've done it differently if I'd known better, and I thought I was doing well! But we really had no clue what would be in store, and the important thing is to pack lightly- you can, and it will absolutely be okay. You never know what will happen, and it will make the trip much, much, much easier and smooth to pack as light as possible.
Sleeping bag pads are cheap (Thermarest's are great!), and a Futon is cheap when you get where you're going. All the stuff you're planning on taking I would not take, -except- some clothes, the sewing machine, a baby carrier, any important papers, and what what will be in the car, and that's it. I know it's hard to leave the other things- it was for us! And I don't have a serious attachment to stuff, but we truly did not need to bring half the stuff that we did. These are my thoughts on what I would do in your situation (doing mine over again in my head, heh). :^) I hope this all helps a little! Have fun, and it really can be a lot easier than you think. Moving is stressful, even if you have one backpack of things, so accept that and smile about it. :^) Seriously, take it as easy as possible, especially because you're going to have a baby soon and the less you bring, the less stress and more joy and excitement there will be. Please let us know how it goes, and I'll keep an eye out for other posts of yours or keep track of this thread, so I can know you are doing okay and feeling good. Good luck to you and your family! :^)