I previewed videos on YouTube that closely matched the way I would birth. I'd send you a list, but it was about 3 years ago and I don't have that computer or bookmarks anymore.
Then I watched them with the kids first without sound and then with sound (the live videos over the slideshows were more helpful, imo) This way the kids got to see what was happening before hearing it - sort of a slow intro to their senses. I spent all this time working with them explaining that I "moo" and how my belly squeezes to open the baby tunnel and mommy doesn't yell. THEN - my youngest was born with a nuchal hand and I totally thought I was going to split in half and I roared him out of my body. Woops. :) But my kids were well-prepared enough (or fascinated, I guess) and they backed up some at that moment, but didn't freak out or cry or anything.
My kids were a little older - 6 and 3.5 at the time of the birth. I would totally recommend planning to have someone come over that is in charge of the kids specifically. This person should not be fearful of the birth and should know what to expect so they can talk your kids through it if they need to, but at the same time, you want this person to be willing to take the kids away if the kids need it too (so maybe your mom would be a poor choice if she is bent on seeing the birth, ya know?) When I yelled at my last birth, it was nice to have someone to remind them that it was OK, normal, almost over etc. And had they needed it, completely shepherded them away.
Mostly you don't want you or dh distracted by having to fetch sippy cups, put in movies or change diapers etc in the thick of things.
This time around I have a 2.5 yo in addition to my now 8.5 and 6yos. I have a few good friends on call (depending on time of day/schedules etc) who will come to sit with my kids and keep tabs on them. I am totally not worried about my older two "veteran" birth junkies, but I don't want them to miss out on things by caring for their youngest brother and I just can't predict his behavior. I may decide he's too much of a hassle and want him to leave. Who knows? My second birth, ds1 woke up and needed love in the thick of things and I totally couldn't deal with him. Luckily I had my parents there and they took him to the other end of the house and laid down with him. He screamed and was upset, but I just.couldn't.deal. with the wiggly 2.5 yo then.
I TOTALLY think its an awesome family experience to have your kids there. I recommend giving them specific tasks they'll get to do too. Like ds1 wanted to hold the baby and at age 6 was capable and experienced enough with friends' babies to do that job. So while I got out of the tub and such, he held his brother. (best part.... dh moved the video camera in the living room for that time period. Absolutely priceless footage) Dd had just learned to use scissors so she got to help cut the cord. They both knew where the birth kit was and were sent to fetch things from it periodically. They LOVED being involved like that instead of random bystanders.
Hope some of that is helpful info. Want them there, hope it will work, but don't be disappointed if they can't handle it and need to leave too.