I don't have a lot of downtime when the kids are here. Right now, not all of mine are nappers, so I always have at least one, plus my own child awake. However, I try to get them to do quiet activities when the other kids are napping, like puzzles, reading books, playdough, etc. That allows me some time to get off my feet and have a breather for a bit. I also don't "entertain" the kids--they are great at playing together, I just supervise for the most part.

I clean/tidy as I go throughout the day, so there isn't much left to do after the kids go home aside from a bit of straightening up. Prep time is very minimal. Every Sunday, I do a quick meal plan, choose where we're going for field trips, and pick out a few crafts.