It sounds like you have a wonderful, lively and intelligent child who needs to be active and to explore. Of course, he still needs to learn appropriate boundaries. That doesn't mean you hit him with a wooden spoon, however!!!

Re. your stepmom and dad... when I travel with friends, I let them know up front that I'm an introvert and need time to myself on a regular basis. If they can't handle my going off for an hour or two on my own, then we can't travel together. I don't judge them if they can't deal with my needs and I don't apologize for those needs.

Similarly, maybe your stepmom and dad can't tolerate a chaotic environment. If so, instead of blaming your son, they should own their own issues. Instead of asking you to hit your child they could explain their own needs and ask to find ways they can still spend time with a beloved grandchild. They could make the effort to be gracious and kind.

Outward good manners are meaningless if they are not coupled with a good heart.