It is fine, HOWEVER, there are a few restaurants that will charge a higher price for over 9's. They will also give larger portions, but they won't charge the kid meal price for what Disney considers an adult.
I've only heard anecdotal evidence, and only heard of one or two places that have made an issue of it.
For the most part, IMO, as long as you tell the server that you have a 10 yo who would rather get something from the kids menu, you won't get a hassle.
Of course, at any pre-plated, family style restaurants, or buffets, your child can get "kid food" with no problem, but they will be charged the adult price.