Hi @Kelley47 I think that @Cole24 is right, have some more time chatting and getting to know eachother before you confirm the booking.
If the booking is for summer 2019, I guess that these particular guests will not be the first to stay at your listing, even though they may be the first to book- and by the time their reservation comes around you'll have built your hosting confidence?
You're right, everyone needs the chance to build their airbnb reputation- guests but also hosts too. Remember you're new too and don't have any guest reviews yet 🙂
The more complete their profile is and more verified info they have the better: phone, email address, government ID so on and so on, this will build trust until the reviews start coming in.
I will forever remember those first few guests who took a (educated) chance on me when I created my listing and they booked- without me having any previous guest reviews!
I am an in-home host, but I have had all great experiences with first time airbnb guests- I find they act on the side of caution as they are new to Airbnb, so they do need explaining about how things work, what's ok and what isn't but then they're fine and have a great time 🙂