We also tended to overpack especially food and still do that today. But always better to have some extra's for that last day meal
You might be able condense cooking gear (and cleaning of such gear) by having a foil meal or two and yes let the kids help cook that meal, they learn about fire. Do not know if toys were included but leave them at home, natures toys are just as good (short hikes on the bike trail, a walk to the restroom near the playground, At johnson branch it is a nice walk to the beach area, look for "stuff".
If you plan to do lots of camping look at a foot locker, just do not over pack it
Try to pack your van so that the things you need first are packed last.
Make sure your tent (and tent pegs plus hammer) and some ground tarps will come out first. Sleeping bags and mats should come out next. then gear and food.