I've experianced a few things in the last few summers..
Buy a good size pool but nothing to huge- you should add fresh water each day you use it, I've tried "saving" yesterday's water in hopes the next day I wouldn't have to add water again but it never worked. So if the pool isn't huge it won't drive you nuts to refill it everyday.
2nd I used a bleach spray once to scrub junk off our plastic pool and the bleach took off the clear plastic coating and the decorative "whales" on our pool are now distorted and I ruined the finish.
Every now and then when the pool needs a cleaning I fill up the pool with water and add dish soap. Lots and lots of bubbles and my daughter enjoys something differnet.
If your really wanting to have a pool ready each day without adding water your going to have to invest in a larger pool that requires a filter and chemicals to maintain the proper water. You can buy one these for like 50 bucks I think and you just take them down at the end of the season.
I think of it as a outdoor bathtub, and I having a few kids float all day and probaly urinate in it etc.. you need new water or a filtering system with chemicals.