those creators in the post above yours are probably a good place to start - not too complex and you get instructions for three models, in case they don't like the main one. Do what that poster did, and dig the pieces out for each step in advance, so your son can concentrate on putting them together.
Jonnyram, I had both those sets when I was little. Rebought 8860 from ebay now I'm older (parents gave away our lego when we grew up..)
I got a mint & boxed 8865 on Ebay for £40 at the end of last year. I nearly wept with happiness, it was my childhood dream set. I'm debating grabbing an 8860 to go with it at some point.