annoying guest wants me to hire a babysitter! help!!

ahhhhhh!!!

so.. at first we wanted a no kid wedding!! then, my fh's dad insisted on bringing his 5 year old grandson from florida, and fh was so excited that i decided to invite him as well as a few other kids from my side of the family to make it fair. i have a really annoying cousin that has a 5 year old and an 8 month old. before i even told her that i was inviting the 5 year old, i get an email asking if i was inviting him because 'he loves getting dressed up and would loves weddings'. so i reply that yes he is invited, but we are not having children under 5 years old.

now i get another email asking what she should do with her baby, if we are providing a babysitter because it would be rather expensive for her to hire one. i'm fuming.

my dad kept saying no kids specifically because of this cousin, and knew there was going to be a problem. i don't even want to tell him, i want to reply to her in the best way possible.

what would you say in response? thanks