The first thing I would think about would be home made things. If you are crafty there are any number of things that you could be doing; sewing, knitting, wood crafts. Baking even-some nicely made baked good used to feature regularly amongst our Christmas exchanges.
Next I would start now, visiting charity shops. I shopped my daughter's entire first Christmas in a charity shop and spent less than ten dollars. I came away with puzzles, a singing Elmo doll, a learn to dress Ernie doll, books....I topped it off with some crayons and play dough and in total I think I spent less than fifteen dollars. You say your kids are grown, so you won't want toys, but there are clothes and house hold goods, books and so on.
Yard sales are good too but time is now tight for them. Watch for sales and coupons, and just prepare people for a small Christmas. Other than that try to relax-it's not all about the gifts. At least, it shouldn't be!
