Is there something funny or surprising I can give to my parents while they're at a resort?

Hey all,

I don't know if my title properly captures the sentiment but my parents are at a resort with my dad's siblings in a few weeks, and I was thinking of some way to surprise them. It's my dad's retirement, and we've already had a party but I'm now trying to think of a way to jokingly surprise him while away. I'm thinking a cake (or similar birthday style celebration where they sing for him), or just something along those lines that I could organize from here but I can't really think of any other ideas. Even a shout-out would go a long way but the issue is I don't have their full itinerary.

I know this is likely highly resort dependant, but I'm wondering if anyone has thoughts on what might be possible or if it's even worth contacting the resort for - I might be trying to do the undoable.