Here is a list and links to things to do in the Inland Empire. Some Free but most have a nominal fee.
Moreno Valley ~
Parks and Rec dept. will be putting on a movie! Every Thursday starting at dusk. This will be lots of fun for the kids! Take a blanket, picnic dinner & they'll have a blast! They say that space is limited so I would get there early if you want a seat! NO umbrellas, popups or alcohol allowed.
Conference and Recreation Center
14075 Frederick Street
Harkins Theatre has a very inexpensive pack of movies to attend for $4.50. They have early show times which is my only grunt about it, but how can you pass up 10 different movies for $4.50. Tickets went on sale in April. I'd run and grab some if your interested!
Jurupa Valley, Ca 92509
Rancho Jurupa Park. A beautiful local camp ground that has play equipment for the kids, tent camping and RV camping areas, and also cute little cabins that can be rented out. It has a convenience store, a kids soak park, climbing rocks with sand and mini golf (golf does charge extra).
Jurupa Mountains Discovery Center