For July 10th, I would say there's likely to be at least a few of my neighbors with their kids, 7-ish seems to be in that wheelhouse as well. Can't verify for certain, but the folks with kids went to this one last year, and it's being put on by another of the neighbors, so it's likely they'll be there. If it's attended as well as last year, kids will be in abundance.
As for the Sandbar Bash in August, that one is likely to be a more adult crowd, but if we're hanging out on the outskirts, we should still be able to hear the music and make it as kid-friendly as we want it to be. Mt Olive is supposed to be the band playing, and I know they tour the state, so there's a chance you may have had the opportunity to see them before, so if you're coming to see the band, you can always move in closer, or off to the side, or whatever.
I haven't had a chance to check out the area they're moving the Sandbar Bash to, but I will be doing so in the next few weekends.
@WiskyDan has some more experience in the general area, but the exact spot the event was moved to is NOT the typical area for hanging out - that seems likely to change if this year's event is a success, as the weed bed can get crowded - in a good way. I met up with Dan this past Saturday, but I had a family reunion to get back to, and didn't have a chance to scope it out.
Just a hunch, the launches on that side of the lake will be swamped for the Sandbar Bash in August. For July 10th, any of the launches on Poygan will be fine. I talked to my neighbor, and he has no issues with letting me park anyone who's coming either by me, his house, his rental unit, or his woodlot a block down the road. Anyone NOT responding to us in this thread or via PM, I can guarantee you won't find easy parking by our launch unless you know another local in the area - the neighborhood seems to be booking up fast with visitors, friends & relatives coming for the event.
For anyone who wants to, afterwards you can pull your boats, or anchor off shore right in front of my place (it's waist deep at most), and we can gather/meet up again and have a fire or join with the rest of the neighborhood - just make sure to bring your own seating and drinks.