Per William's comment, I don't think they have anything to modify. Awards are for 2 guests, but US properties (in nearly everyone's universal experience) don't charge for kids etc. unless you want extra beds and even then not always.

You should take the advice above and, after booking, call up to have the children added to your reservation. Or just book it on the phone. That way you don't have to worry about showing up with 4 people for a reservation that says two. Case closed.