The London Mozilla Festival has a Youth Zone full of Fun, Quirky, Geeky and otherwise interesting workshops for young people aged 8+
I cant recommend it enough for anyone into Science, Maths, Raspberry Pi to Making stuff and Art, who want to experience workshops designed by youth for youth and the young at heart ;)
We are attending on the Sunday as Sabrina is leading her first open public session remixing Manga with ibisPaint
The festival is held at Ravenbourne college London O2, it's a festival that goes out of its way to be inclusive - In 2013 I started the Youth Zone with my MineCraft coding kids club there and have now handed it over to the very kids that played Minecraft.
Youth tickets are only £3 and sell out fast!