Have a read of this : http://www.anstonftc.co.uk/entering-hft-competition/
and come along to the NEFTA Hunter Series - I think you and your son will really enjoy it!. In fact I know you will.
The first event this year is at York FTC on the 11th May.
Keep an eye out for posts about the event closer to the time on here.
The NEFTA Hunter series is just a nice fun introduction to the world of HFT, although you will find series Champions and World champions taking part in it, the atmosphere is light hearted and welcoming.