When our 3 children were 4 and 5 we took a trip into Canada. Our youngest daughter wanted to learn how to swim so dw took her and I worked with the other 2. Anyway, she started to fight dw and kept telling her to let go, so dw did. When dw pulled her out of the water she was spewing water and crying and yelling "You let go of me!" It was just hilarious, even now, 30 years later, we will all still laugh about it.
As for kid friendly parks, they are almost nonexistent. We stopped at several Jellystone parks thinking they would have great things for kids to do, but they only had swimming pools and maybe a swing set.
Hope your trip goes well and you create fond memories like we did when our children were growing up.
Berniece & Russell Johnson
Lil'Bit, a Netherland Dwarf Rabbit
1987 Southwind
1995 Ford F150 Supercab
Life in the fast lane? No thanks, we will stop and smell the flowers at every opportuity