Yeah, more info is needed here.
We are about to paint the interior of the house next week, and we've painted the inside of a house before with young kids. Here are a few thoughts:
1) hiring someone is going to be really expensive, especially in today's market. We have a lot of walls to paint, and the quote we got for walls and trim was something like $8k. We figured the materials cost for us is going to be about $2k, including Sherwin Williams paint.
2) why would you need to leave the house for a couple of days while the paint dries? Do you have a sensitivity to the fumes? Latex paint dries in a couple of hours, and by all accounts isn't hazardous.
3) why do you need to exile the 1-year-old? There are lots of ways to manage kids so you can paint, without hiring a sitter.
4) high ceilings over stairs are indeed a challenge. I plan to build a platform that screws into the (carpeted) stairs, on which I can put a ladder, in order to reach the top of the wall.
5) being in good (or even "reasonable") physical shape will help tremendously, particularly core strength. If you don't currently exercise, I'd recommend taking steps to improve your tone, so that you don't suffer as much after you paint.