Just an FYI...the only way to get the Fantasmic tickets for each person is to pay for a package dinner for every person over age 3...so having your two kids share a meal will not work (you'd only get one ticket for the one meal paid for, so they'd turn you away when you showed up with an extra child...they are strict about enforcing ticketed entry at Fantasmic. The only child who does not need a ticket for the reserved seats there is the baby.)
AND, the info about "ala carte ordering" does not mean quite what you're thinking. The reason you see that reference is that it used to be that Brown Derby & Mama Melrose had a special limited menu just for the dinner package: it was a set menu for a set price. That was changed a couple of years ago...it is still a set price for the package, but now you're allowed to order any appetizer, any entree and any dessert off the regular menu--that's where the "ala carte" ordering info came in. HOWEVER, you only get what you pay for...so if you buy an adult dinner package, you order off the adult menu...if you buy the two kids' dinner packages for your two kids that are over 3, then they will have to order off the kids menu at Brown Derby or Mama Melrose -- the "ala carte" does not mean they can choose anything off the menu--just anything off the kids menu. They won't be allowed to choose adult entrees, etc. If you really want them to have the adult choices, you would have to list them as over age 10 and pay for the adult packages (and even then, they can't share because you'll have to purchase two dinner packages for each of them to get a ticket.) Last time we got the package, I think Mama Melrose was $39 per adult and Brown Derby was around $45 per adult; that was last year though, so the prices have probably gone up. Have you looked at the kids menus for the table service restaurants? In general the table service kids choices are better (and more varied) than the counter service places...you can usually get something besides just chicken nuggets at the table service places. Side dishes for kids are usually better at the table service, too.
Probably the most reasonable option that would allow your kids to have adult entree choices would be the Hollywood & Vine buffet...there is a kids buffet section, but they can choose food from any section of the buffet.