im making this simpler, and buying them bitcoins

(paper wallet inside a card

)
Surely $/£50 worth of bitcoins is better than a gift they will forget about in a few days.... and one day they will be telling people about the best Christmas gift they every received..... (now worth $/£5000....)
Yeah, as long as they don't lose it or just look at you like you just gave them monopoly money haha. But yes, it's a nice gesture and possibly a great investment. Just make sure you tell them that and print a wallet out that briefly explains what BTC is and how to use/redeem it.