I have no idea what to give my parents as a gift...

They are super amazing and have been so supportive and loving and generous through this entire process. They have spoiled me terribly and just when I think they're done spoiling me, they offer to pay for something else! They are amazing and there's no way I would have been able to do this without them. What kind of gift could I possibly give them? It needs to be heartfelt and not necessarily expensive because they basically just buy anything they want. LOL
I love and appreciate them so much...what can I possibly do!?
(One thing I'm doing is having our band play their wedding song at the reception because their 30th anniversary is 10 days after my wedding....but that's just not enough!!)