I never fly Delta but we order Kosher when we fly. We're Jewish and just don't eat pork, but it's usually pretty "kid-friendly". You don't have to be kosher or even Jewish to order it. They also wrap everything separately so they can be tucked into seat pockets and eaten later.

If you opt for this, tell the F/A that you're not religious and that they can unwrap anything without your approval (we would have to "present" the meal to them, avoid that!)

I worked for another major airline and many of the parents complained that the children's meals were "greasy". Often, there was nothing fresh (i.e. salad) on them.

Be sure to mention it IF you reconfirm (I wouldn't call specifically for that but if you do...) at again at check-in.

Once ordered, it is your meal. You wont have the option of his taking a "normal" meal instead. You can ask if there are extra regular meals but you need to wait until everyone is served to see if there are any left.

If you opt to at least bring some of his familiar fare, remember that there are no microwaves on board. To reheat food, it needs to be in a sealed container that can go in a convection oven. Just wrapping it in aluminium foil will do the trick!