+1 for quad-biking, afternoon in a nice warm pub thawing out, followed by Michelin starred restaurant would get my vote. After that you are on your own.
Other ideas:
Winetasting at vinopolis
Snowboarding lesson at Snow zone
Youth hostel and a hike in the dales
Trip to Afan for bike riding and warm pub
Clay pigeon shoot – great fun and I’m hopeless at it!
PAINtballing – if you must, my 13yo lives it.
A mix of outdoor activity and a quality meal would get my vote every time. If I were organizing, I’d pick the quad-biking again, it really was very good and not as technical as a bike ride might be.