As for during the day: Does your daughters day care "need help"? Let them earn some Summer Cash, or at least a valueable lesson in community service. (If the day care won't pay them, make the job part of their allowance.) If her day care doesn't need the help, I'm sure a local church/ sinagog (sp?) does. Do you know any of the neighbors with kids their age? In a few weeks, this will be a great option, especially if any of those kids have stay home moms.
As for at night: have a TV free night in. Take out your favorite board games, print mad libs from http://www.madglibs.com/ or make up a new version of an old game. For example: before Balderdash exsisted my fam. would open the dictionary and read a word. Then everyone would guess what it ment. OR- We'd tell them what letter it started with and give them the meaning, then they'd try to guess the word. It sound lame, but we used to have a lot of fun. Another easy one to copy is Scatagories. Have everyone 1 or 2 "things", like "boys names" or "Type of Sandwich" and everyone writes them down. Then take turns choosing the letter that starts each one (for the 2 examples, using the letter B: Bryan, Bologna) and set a timer for 2 minute (more or less depending on skill). Make sure everyone has the same list before you start. The object is to stump the others or come up with something SO obscur that no one else could posibly guess it. They can dispute it and kick it out if it's not real. (Like a Burboned banana and brown sugar sandwich. Might exsist SOMEWHERE, but probably not real.)
Be creative and have fun. BTW: I love doing "pizza picnics" at the beach. Something fun I did with some high school chums that was inexpensive but also fun: draw names, go to the Good Will, or other second hand store, and by the person you drew an entire outfit, the more hideous (sp?) the better. Now, EVERYONE has to wear their "new" outfit as you go out for the night. Take Pictures of the adventure. You WILL laugh, you WILL be embarassed, and you WILL always remember it fondly!
Enjoy your summer~ J.