Compartmentalize and Consolidate
We maintain you just can't be too organized. And when you're traveling with the family and constantly rushing to unpack and repack, you should be able to pull out the toothbrush quickly, and without having to unpack everyone's clothing.
Most importantly, it helps to separate toiletries from clothing. The plastic zip-top bags we mentioned earlier will do in a pinch, but a compartmentalized toiletry case would be even better. Some even hang conveniently as shower caddies.
And consider consolidating the family's toiletries. Sharing, if possible, will simplify things, and make for a lighter load.