We did gift cards for £50 per card you can use at various restaurants for 2 weddings we went to last month. We didn't feel comfy putting cash in an envelope and thought it would be nice for the newlyweds to have a date night on us x
I would get one of them gift card you can use at restaurant and shops . Like one card . Just to give them more options
I personally just put money in a card so they can do what they like with it? £50 is definitely enough though 🙂