screen cabins - yes (unless you want to get eaten by bugs)
Bugs - bad enough that my wife won't even stay in the cabins
mini van/trailer - probably (unless there has been some washout since last year)
Newbies - last year we had some complete newbies rowing rented rafts. (no children however) they did fine for the most part. Kids would up the ante in a pin/flip/missed eddy situation. would probably consider having the kids in a boat w/some experienced folk. While most of the river is pretty easy there are some rapids that would require some caution.
Tips - ? too young for pbr, maybe nyquil. Sunscreen, bug juice, a fishing pole, lots of benadryl lotion!
Have fun we may see you there! 7/6 launch.