Nearly 10 years old and still bedwetting most nights

[castle]

You are not awful!!
The fact is that without the cooperation of his mum, it's unlikely that anything will happen until HE wants it to.
I suggest taking him to the GP (or better, ring the GP and speak privately about this first) and asking for a referral to a urologist, preferably a paediatric urologist. REally jump up and down about that, say it's gone on for far too long and making the whole family miserable. It may take 4-6 months to get an appt, but ask if the GP can ring and get you in sooner.
In the meantime, since you've got all the pyschological issues going on with him and his mother, I suggest that you stop trying to do anything about it...at all. Buy the dry nites (yes I know they're expensive), use the pinky and do what you can to avoid the laundry. Just make sure he puts his own dry nites in the bin. NOTHING that you or his dad can do will make him want to use the toilet at night, or it would have worked by now. So just let it go. This way, what you two and his mother do will be more or less the same, so there will be fewer conflicts too
The urologists, especially the paed ones, are used to dealing with this sort of thing. Trust me...they've seen every problem under the sun. They may say he needs a psych referral, but I think they'll want to handle it themselves. Let the plan of action be between him & the doctor as much as possible. Tell the specialist everything. Usually you can say that you need to talk to them before he is seen, or just after....say that it has to be a private conversation.
General opinion would be that if bedwetting is going on by age 10, no matter what the reason, a urologist's opinion is a good idea. This is because there is heaps of research over the past 10+ years which have shown that many of our old ideas about bedwetting & bladder/bowel control problems in general are wrong. Most problems which were thought to be totally psychological are now known to actually be physical--even when there are psychological factors too. In other words, there may well be some sort of physical issue going on with your SS, although if so it must be minor. Anyway, that is something for the urologist to sort out. This is why you need to get a referral. Your GP may or may not be familiar with this stuff. Also, it will probably make more of an impression on your sson if the specialist talks to him, rather than the GP.
Also, just to add, I found the urologists to be much more help than the paediatricians. This is their issue and they know it inside out. (We've moved around a bit, so have seen 3. All excellent.)
Don't punish your SS. It hasn't worked and it won't work. As far as the school camp, just let him take his dry nites. He'll be able to change in the bathroom. If he wears boxers or pyjamas over, they are really not noticeable. In the morning, he will get up first thing and put them in a plastic bag, and then either bin the dry nite or save the bag to take home (yucky I know....). The thing is, either way the other kids probably will not notice.
My oldest DS is nearly 13 and still wets the bed. He has a diagnosed problem which is 24/7 and well under control. Now we are only dealing with the night-time, but like you I am "so over" it. It's because of his problem that I have learned so much about all of these issues.
Please pm me at any time if you have more specific questions, but I do really urge a visit to a urologist. HTH a bit!!