My dh travels a lot, and my kids are 4 years and 13 mo. Because he does travel a bit, we are now fairly accustomed to it. While I always miss him, there are aspects that I honestly look forward to when he is gone...
As others have said, quick and easy dinners! My 4-yo loves to help, and we make things like scrambled eggs, quesadillas, pizza (our local pizza shop will sell the dough, the we just have to roll it out and put on toppings), mac-n-cheese...we also often scour dd's children's cookbooks and make "creative" meals together - dh might not like a dinner of penguins (made of dates stuffed with cream cheese) marching across cottage cheese "snow" but the kids do!
Earlier bedtimes and leisurely baths, etc (when dh is home, we wait for hiim to get home from work so we can all have dinner together, so the evening is shorter after dinner)
After the kids are in bed, I have a long quiet evening to work on my own projects - sewing, writing, knitting, etc. This is the time of day when I miss dh most...but I LOVE getting time to do all that stuff!
Somehow,, when he is out of town, the laundry is dramatically lessened and certain household chores are not as pressing...
Things I like to do to help make it easier for all of us when he's gone:
Schedule a playdate or two, preferably a playdate where mom comes too so I get to socialize a bit!
Have one of our neighbors over for dinner - the company is nice, the kids have fun, and daddy's absense is not as "visible" when there are others around to play with and talk to.
Dd and I do what we call "special girl time" when dh is not here - I try to have some special crafts or activities ready to do together - making beaded necklaces, baking, reading a new book, maybe opening a new craft kit or something...making it an opportunity for connecting and doing something special together. Once ds gets older, I'll do this with him to, but we'll have to call it something different!
We had our first "movie night" on his last long trip away - early dinner, pjs and slippers and bathrobes on, and then we cuddled on the couch and watched Charlotte's Web - a big hit with my 4-y-o dd! (Ds played for a while, watched and cuddled a bit, and then I put him to bed and finished the movie with dd). The next day, we started reading the book and finished it the day before dh got home.
When bedtime with two is looking like it might be a struggle, sometimes I bundle both kids up (pjs, followed by all sorts of winter layers) and bring then outside for a "star walk" in the evening...they ride in their cozy sled, all bundled in, and I pull them, usually on snowshoes and into the woods...it is a big adventure, and it feels really late since it is so dark. We watch the moon and the stars - we live in a really rural area, so it is dark and quiet. Sometimes they fall asleep before we get home - if not, they are usually pretty mellow and ready for bed when we get home. The last time we did this, both kids brought a sippy cup of warm milk with them, so we brushed teeth when we got home. Dd wanted to brush her teeth in the dark, and did not want to turn on her electric toothbrush "so I can just keep it all peaceful, like outside"
Outings help - to the library, a museum, ice skating, sledding...something to look forward to each day.
That is all I can think of right now - good luck!