Surely you can’t “send him” when he’s 18? Would he go?! I stopped being able to send my dd anywhere when she was 14.
This year I would have loved for my dd to finish her watersports instruction certificate but it was a hard “no I can’t be bothered.” I’m not going to force her. When she’s 18 and has no money to go on holiday with her friends she’ll realise she should have planned ahead and then she’ll be stuck scrubbing round for scarce crap jobs in retail instead of spending her summer on the water teaching kids stuff she loves.
Perhaps I’ve gone too far towards letting her decide her own path - but I can’t complain that she is shy. She oozes self confidence. On the other hand she is lazy and entitled.
Your situation is different. My first thought is that perhaps you have been too domineering or prone to infantilising him, albeit not deliberately.
Why do you need to “cure” his shyness? Is the job needed to earn money (Camp America employees from UK don’t do much more than break even)?
There are residential jobs at PGL for summer camps in UK. It’s akin to slave labour but if you want to be toughen him up or he wants a career in sports and leisure its not a bad idea.
I think you should leave a space for him to work it out for himself though. He’s almost an adult. Ask if he’s had any ideas, help him if he asks for it, offer input if he’s totally stuck. But don’t “send him.”