IMO,It is not necessary to notarize the consent form for your child. Understandably, you can sign on behalf of your underage/minor child. I have a 3year old baby and I consented on her behalf without having to notarize..
I am actually in a similar position. I received payment instruction by mail, paid and sent in confirmation on Feb 1. No response regarding shipping label since then. The whole thing is pretty frustrating!