As per any fetish he will probably have 'specific wants' from the session.
Maybe stuff he likes, maybe fantasy.
Discuss as adults -- no baby talk allowed.
See what is and is not acceptable to you.
If stuff grosses you out but is important to him, improvise.
Like if he wants to be a pooy baby and that grosses you
then fill his diapers with mushed up bananas or similar,
for the same effect for him but without the smell and gross-out factor for you.
{assumption on my part: Even my own poo grosses me out so much that I blindfold myself when I go to the bathroom!
}
Weekend booking? As a first meeting? Possible.
But with such a thing being a big ticket number (whatever you charge for 48 hours +)
A big, big chance this is a fantasist.
I suggest taking a deposit of say 20% just to see.
(use search facilities to see methods some of us use)