(((Giabrina)))
I agree with the tips from others!
The library has all sorts of activities for children nowadays, and it's free!

I applied for scholarships to our YMCA for my girls to attend daycamp & was awarded 2 weeks at half-cost. I could only afford 1 week, because it was $100, but it ought to be a great week for them.
In my area, we do have a couple of movie theaters that show kids movies once/week for free during the day. Something different to do...
Of course, there are lots of parks to take advantage of as well. Lots with beaches for kids to play in and keep cool. Some are free, others cost a few bucks for parking (or you can buy an annual parking permit for county parks & that pays for itself real quick! I think that it's $30).
Play at home games I can think of: water balloon fights, "jump through the hoseline", slip and slide, hide and seek, finding hidden objects with lists to scratch off, arts and crafts, etc.
Hope that you've got some helpful ideas that work for you and your kids. Best wishes to you!