Firstly - hey, I'm also 14th September 2019!
Secondly, whilst I'd be tempted to book, I'd have a sit down with him and ask why he doesn't want to check it out. Explain to him that you can't guarantee the venue will still be available after Christmas.
Is there a reason behind his lack of enthusiasm - maybe he just isn't fussed, or is it all going ahead a bit quickly, and maybe he's feeling a bit overwhelmed?
Is he worried about having to pay out a large deposit on a venue right before Christmas?
If he wasn't included in the initial choice and visits, maybe he's feeling a bit rebellious? My fiance and I went to visit all of our venues together - if he'd chosen one without me, I'd probably feel a bit 'yeah, whatever' about it too.
Have a chat with him. Just booking the venue will exclude him from the loop even more, and could put additional strain on your relationship. You might think it's the perfect venue, but he needs to want it too.
Good luck! X