The Cadets are a Youth Organisation sponsored by the MoD. It is a blurry distinction, but a distinction never the less.
Likewise, the Armed Forces are NOT exempt from discrimination rules... although you are unlikely to find a blind recruit, but then would you find a blind trainee fireman?
Your form, complete with the offensive 'Christian' wording has probably been knocked up locally at your kids local ACF Det. i appreciate it is still the 'face' of teh ACF, but it was probably knocked up years ago, and teh adults of the ACF det just never had the time to a. think about something so mundane or b. they are older and it just didn't click.
Rather than dropping digs in on the internet, why not mention it to the ACF adults at your det? At least give them taht much of your time.
Maybe even offer to give up some of YOUR time to help them out. They are all volunteers, they give up their time taking your kids away. I am sure they would welcome someone giving up a few hours to go through their forms and do some photocopying to help them, after all many will do a full time job and then anything up to 6 hours with teh aCF per week. Not to mention weekends and holidays.
You could find you enjoy it, and you yourself become an AI. I had a 50 odd year old woman join as an AI, because her kids had. She'd never had contact with the forces before and loves every minute of it.
Re Cadets, ALL Children can join, there is no medical barriers. There are many Cadets who are disabled and still enjoy the ir time. That said, sometimes you are going to have to accept that not ALL kids can be catered for.
If the kids can't inject themselves, who can do it? An ACF Adult can't just stick a needle in to a Cadet. Larger camps usually have Nurses with them, but if it is a small camp, perhaps the medical issues are too great.
I've often been canoing on a lake with a big waterproof bag of meds.