Need information for Pittsburgh trip kids NEED fun?

I am trying to plan a trip to Pittsburgh with my kids. We want to go to Kennywood, the zoo, and the science museum. I need to find cheap but good accomadations and tickets. I am planning this for July 6-8. I need hotels for handicap people and my kids want a pool of course. I want this to be fun and unstressful. My kids are 15 and 10 and my 15 year old this will probally be his last vacation with us as a family he will be 16 soon and will get a job soon. Please help a family in need of a serious vacation. I am also disabled with fibromyalgia so I tire easily and have problems with walking and my back. My kids and I have not been on vacation for 3 years since my brother died. We have had alot of deaths my brother, father and both my grandparents all within 3 years time. My kids need to see fun to have a good time and not worry all the time as they do about me. My kids are always worried about me but I want to show them we can still have fun and they need not worry.
I can not drive for long distance. I live in Erie and our zoo is small. It takes maybe 1 hour to go through the whole thing. Nothing is there it is just close to us. Kids really want Kennywood all we have is Waldameer up here not a big place at all. we go every summer to there the kids want something different