Low cost Spring break activities

I took off for the week and had planned activities for outside, but it’s gonna be rainy and not so warm. Anybody know of low-cost activities I can take my 4 and 6 yr old to. Mamma’s on a budget and Children’s museum, Sloomoo, Dino dash, etc are a bit pricey. We probably will do some bowling because I have a Groupon, but any other suggestions???