The week after Halloween is the best time to buy dress-ups for your kids for Christmas (or for birthdays). My friend was able to buy all 3 of her girls a princess dress for a ridiculously low price at Wal-Mart.
And if you need a gift for a boy buy a pirate, cowboy, police officer, or soldier costume after Halloween for them to dress up when they play.
If you miss the Halloween blow-out sales you can always make dress-up costumes whether you sew or not. It doesn't have to be a lot. Just an eye patch and hat would be awesome to dress up as a pirate.
Besides giving costumes to kids you could also give a variety of costumes to grandparents. They might appreciate some new and exciting things for the grandkids to do when they come to visit.