I think that this would have been a stronger letter if you'd left out the bit where the kids' drinks cost $13.14. They cost $13.14 because there were 6 kids, not because they were ridiculously overpriced. In addition, you'd already pointed out that the drinks cost $2.19 each, and that's really the price that matters: otherwise you would deserve cherries more than a customer with 3 children but not as much as a customer with 9. I think we can both agree that the restaurant shouldn't have a policy like "If you have 7 [or 5, or 10] or more children in your party we will put cherries in the Shirley Temples."

If you'd done that and used lower-case letters where appropriate, I would be complimenting you on the this letter without reservation -- I really especially like that the waiter who told you you couldn't have something that you wanted didn't get described as "rude" for that alone, and that you are capable of seeing the cherry issue in context. A surprising number of people turn out not to be able to do that, and I think it's so sad that they miss out on all the good parts of events when one thing doesn't go their way.