Check out http://www.united.com/web/en-US/cont...l/default.aspx ::

"Child: This meal is available for children from 2 to 12 years of age, and includes food offerings which appeal to children. The meals planned for United follow Recommended Dietary Allowances for children."

"Where does United offer special meals? … Special meals are available in premium cabins on domestic flights with scheduled meal service between: … The continental U.S. and Hawaii"

"If special meals are available on a flight, you will be able to make a special meals request during the booking process after signing in to your MileagePlus account. MileagePlus account holders can also add special meal preferences to their profiles for use with bookings made through united.com. When signed in to your MileagePlus account and making a reservation on united.com, if you have a special meal preference set in your profile, you should verify that the correct special meal has been assigned to the applicable traveler’s name prior to confirming the reservation."

I recommend calling United and asking them to add the request to the reservation (then maybe calling back later and confirming that it's really there, depending on how certain the first person sounded). Given the recent changes to online traveler profiles (you can't make many changes to travelers' profiles after booking, apparently a TSA requirement), it is probably worth calling.