Muay Thai/kickboxing, it was not my first choice but we checked out Brazilian Jiu Jitsu for a free session 1.5 months ago and it didn't sit well with my daughter or son. So I have a sparring partner built right in, too bad he's kicking this old man's arse. It's an awesome experience with him, daughter initially wanted to participate but the BJJ and grown men grappling put her off so we moved on to kickboxing instead.
Full disclosure I've been arm wrestling my son on and off for years, never let him win and he just 0-2'd me last week with my full effort. The tide has shifted, I'm expecting sore legs and a black eye next.