Al, go to your local party store - there will be a huge luau section, I guarantee it. You can find everything from really cheap leis (get a pretty flowered one for her) to tiki torches. You can get "sandbox sand" from your Toy R Us store and dump that around. (That's teh best sand but kind of expensive. Probably Home Depot will have cheaper sand of lesser quality.)
If you google "party ideas luau" you'll find tons of pages with much better suggestions than I can come up with!
Happy birthday to her from us!