Are you sure you can't talk them into doing Secret Santa instead? $50 seems like an awful lot of money to spend on a generic gift that someone may or may not like. We draw names in DH's large family, and we also each fill out a card with 3 suggestions of things we'd like to receive that fit the predetermined price range. Maybe it's not quite as much of a surprise, but we still don't know exactly what we're getting or from whom we'll receive a gift.
Hrmm... I am trying to think of suggestions for your situation, but it's really hard to think of many good gifts that aren't gender-specific in some way.
What about a gift certificate for a massage?