From someone who has been to many of these, with kids, I can assure you it is not too much structure. Also Twin Grove is a great campground for kids! You will spend most of the day cruising the trails with group of similarly capable Xterras, and the pace is usually pretty laid back, with plenty of stops, where you can get to know people and hang. Paperwork is simple, a waiver for the club, and you gotta do the offroad parks paperwork(which AOAA I believe you can do online, Rausch you can print-up and home, fill out and bring with you). You dont have to do all 3 days, as for locations, you either drive to one, or the other, they are both in the same area. You do have to show up in time to leave with your group, yeah. But as for the saturday night dinner, its better to get there on time for the raffles and food, but its not like be here at 6 or be turned away.
Also, I run Notajeep4x4, and something new we are doing for this year is a meet and greet BBQ on Friday night, at the campground, the start time says 7, but show up whenever you want, as long as we are at the pavilion, you are welcome! We will have burgers and dogs, etc, BYOB. Planning on having some coloring pages for the kids and might raffle some swag off. Everyone is invited, there is no cost, and this is going to be a family friendly event!