I have put one in a bin then attempted to bury it - before it stalked out the bag to say 'hey I am not dead yet' !? so they can be hardy and very good at impersonating sticks - but you know your son best so if it is possible visit a pet shop or zoo to see what interests him and seems appropriate. A friend of mine is getting giant cockroaches - stripy ones - they are hard to kill not even nuclear war will faze those buggers!
Stick insects? Cheap to feed as they live on bramble and oak or ivy - just need a tank and a couple of stick insects they live a year or so and are interesting for children - you can let them walk along your arm and stuff.
DS who will turn 7 on Monday is very difficult to buy for. He is Autistic and has very limited interests of transport and gardening. He has just come home talking about mini beasts so before the novelty wears off I would like to encourage this new interest.