We use the 18can Polar Bear backpack.
If it's really full with food, it can be pretty heavy. So
weight is an issue. After I fill it to a reasonable weight,
I fill it with something light but I fill all the space.
Agree with Colleen about the dry ice. Get your stuff
super cold and discard any remaining ice just before
you pack the car. Don't open the bag for any reason
other than a curious TSA agent. Stuff will be frozen for
a long time.
If you're not sure about a vacuum sealer, just borrow
one from your neighbor. They really are pretty cool and
I really like the idea of sealing up the little liquid toiletries.

Having said all that, the stores in Virgin Gorda are getting
better every year. This spring I'm going to do more local
shopping and try to compare quality and selection a little
more closely. It may be to the point where all this may be
unnecessary. We'll see.

Mike
Trying to be the man my dog thinks I am