Birthday party invitation

I’m designing an invitation for a surprise birthday party. How do I indicate that the people don’t have to bring a gift, but that a card would be welcome (without being this wordy)? I think a few of the people might bring gifts anyway, but I don’t want the others to feel obligated.

I think a simple “no gifts, please” is appropriate.

Or to be cute: “In lieu of gifts, hugs and kisses will be accepted.”

Maybe you could say, “In lieu of gifts, we will all be signing a memory book” or card or something. They’ll get the picture.