I'm not going to say if it is right or wrong. But, I do have these comments: I chose to use credits for my then 7 year old for all of his meals just as I did for myself, DH and DS (then age 10). My 10 year old loved the idea of getting to choose his own appetizer and dessert for every meal (a lot of food was wasted). It was just easier to let my 7 year old also get an appetizer and dessert of his own choice, also. Everyone was happy. I believe everywhere we went had those offered on the kid's menu. Paying for a kids app, meal, drink and dessert would end up costing us a good bit. With DP, we would NEVER get apps. and dessert. Maybe one or the other. It was just so much less stress to just use the system as planned and let trying to work the system go.
Honestly, I think the dining plan provides SO much food that while it is nice to "splurge" and try different things, it is just too much food for anyone to consume. I don't know that we could have eaten any extra meals. I can see if you want to go to the 2 TS restaurants/shows. We didn't choose any of those.
So, I think the way the plan is already set up is plenty of food without trying to get additional meals by saving child TS credits.
But, if that's what you want to do, that's your call. Disney knows what is going on. Several guide books and sites suggest doing it, so it isn't like Disney is being fooled. They could fix the system if they wanted to.
BTW, I know many don't like the age limits for meals, but my last year 10 year old (now 11 year old) LOVES it. He hates ordering off the kids' menu anywhere. He doesn't eat the full adult portion, but now that he is a tad older he prefers to order more grown up foods. Oddly, this did happen around age 10. I'm glad he doesn't HAVE to order from the kid's menu.