IFPA website will be your best bet for seeing tournaments/leagues, etc until someone local chimes in.

https://www.ifpapinball.com/calendar/

Put your location in the search and it'll generate the info. I would just assume anything held at a bar would not allow for kids to play but other places should be good and you can contact the event organizer to find out.

I definitely recommend having your kids play as soon as they can, especially 8 and older. Just be mindful as to whether or not they're ready to play in a super competitive tournament vs casual torunament/league. Pinball players run the same spectrum as people in life and some don't care for kids playing in events much less being beaten by one.

My 2 younger sons(8 and 11) play in our local league. I just let my 8 year old play because he has not been ready to play. My 11 year old has played for over 3 years but probably could've started sooner, since hes already ranked in the top 800. I really think the social aspect of playing too is extremely beneficial. Good luck and definitely post after your first event.