My son entered a couple of different club level competitions in Northern California. They had several levels, based on skill and not age.
There was the beginner level where the most difficult trick was limited to a 180
The next level up had full 360 as the limit and no inverts
The next level included inverts and 720s
they had a "pro" level but I havne't seen anyone in that level at the club meets.
My advice for you son is to work on clearing the wake before working on inverts. FInd a club meet that has a beginner level and go for it. The best thing he could do is to enter at a level where his tricks are solid: if he can't do a 360 reliably enter the class where 180 is the limit.
Before the competition, work on choreographing a sequence of tricks and practicing that. It is one thing to be able to do a certain list of tricks, it is another to be able to do as many of them as possible in a short distance.
What will help his overall score the most is if he can do tricks going both ways across the wake. Instead of doing a heel side 180, surface 180, ease back across the wake and do another heel side trick he should do a heel side 180, then a switch 180 back the other way.
To be comfortable in the competition he should practice his routine at speeds plus or minus one MPH. Change the weight in your boat. Do it in choppy water. You don't get to ride behind your own boat so I can assure you it will be different, and whatever the conditions are that's what you have to ride in.
A lot of the competions are two pass and they will allow one restart on the first pass. To take the most advantage of this he should start with the easiest tricks first, then throw his most difficult (greatest chance of falling) as the last trick of each pass.
More than anything else, he should have fun at it. Don't worry about falling, don't be disappointed if he comes in last. It isn't about winning, it is about competing.
Good luck, have fun.