check with your local library (or any you are eligible to join-we live near a university and are eligible for membership as a community member) to see what they offer for checkout beyond books-
musical instruments
power tools
appliances
recreational equipment
seeds (free) and planting tools
camping gear....
many, many other items all free for check out.
the same libraries often offer free day passes to area museums and parks (state parks).
if near a university see what free/low cost opportunities exist-
cost of visiting a rock climbing wall place near us? $20 per person. cost of visiting the university rec center? $8 per person (up it to $12 and you get access all day to the pools, ice skating rink and fitness center). kids want to swim during the summer? community pool charges $4 per person, university offers a family pass (no limit on family size) for 10 visits/$64. shoot-for $65 a month a family (again-no size limit) can get an annual pass that allows unlimited pool, rock climbing, ice skating...that's a pretty frugal price to entertain kids.