K.S.
My son and I did a 5200 mile driving trip, camping in 8 different National Parks. Here is what worked for us:
We sorted everything by category. We each had one small clothing bag. All the rain gear and snow gear were in a separate colored bag. I used a plastic bin for all the food, another plastic bin for the cooking gear, and a bin for toys/books, and I had a cooler for cold foods. I had 1 laundry bag for everything dirty, since we were gone 3 weeks we had to do laundry numerous times. We put things away where they belonged every night. Except for our sleeping bags, tent, flashlight, sleeping pads, and one book each, everything else was packed away in the car as if we were leaving. In your case, I would bring 1 mesh bag for all the beach gear and make sure it gets put away each night. Another tip is for when you are at home deciding what to bring. Set out everything you THINK you need and then trim it back by 1/3 at least. Amazing what we can live without.
When we woke up in a lake of rain water our 2nd to last night, this organization really paid off. In the dark at 5am, I was able to tuck my son in the car and "break camp" in 20 minutes (in the pouring rain) knowing I had everything when we pulled out of the campsite to cross the mountain pass.