I ordered my bags early too - and just estimated on who I thought was coming. I ended up being pretty close - but we do have a few extra bags.
As for the kids bags - I put some water toys, bubbles, we made a coloring book, crayons, a "flowergirl" custom tank top for the girls, stickers, etc. - just random junk.
The guys liked the koozies (though no one really used them during vacation), lip balm, sun screen, aloe, and some of the meds I put in there - advil, pepto, etc.