An ideal Birthday present...?

It is a few weeks until my only sister's 30th birthday. I was out of the country for her 21st, so want to get her something extra special for this one. The problem is that we are chalk and cheese. She is married, with two children and works. For other birthdays. Christmas etc. she generally asks for things that are really for the whole family. She really isn't into fancy perfume or cosmetics, or even fancy clothes or shoes.

I am at a real loss at what to get. I even asked her and she said "You coming to the party is enough of a present for me" (she is a master of the guilt trip).

Any ideas would be helpful. I guess the budget would be up to $500.