R.J.
Hey, K. ~
Congratulations on having two healthy, active boys! I have two boys myself - although 4 years apart - and I know if I tried to keep them from roughhousing during the day I'd never get anything else done! My older son is like yours, very kinesthetic and affectionate, and my thought is this: as long as his little brother is okay with it, why should I stop it? Kids are going to get hurt because they're kids, and hopefully letting them do it in a safe, supervised environment will limit the physical damage when they're elsewhere. Plus, it gives them an opportunity to learn empathy for one another, and forgiveness when they are hurt. We have had to devote quite a bit of attention to my older son's physical interaction with strangers, but that is an entirely separate issue.
It sounds like you're doing a terrific job, K., letting your boys be boys while still protecting them. Keep it up!
~ R.