Other people have mentioned it already, that food aside (all the work, and all the cost) you still have the logistics of having that many people in your house, seating that many people around the table, having that many chairs, having enough cutlery and glassware and all the different types of plates... Then the cleanup at the end...
It's a lot just to host, forget the food, just to host is a lot!!
If and I mean only if you still absolutely have to do this, and please keep in mind that they're not forcing you, you're doing it to yourself, and I'd recommend that you get yourself out of it when you still have almost a month to change the plans...
But if you have to do this, make it on the provision that you host with the venue, but everyone else brings the food.
Everyone else has to bring a main, a side, and a dessert item, as well as one drink ((bottle of wine, non-alcoholic, etc.)
This is going to be so much juggling so much confusion so much work, I doubt your guest would even want to come, but at least it takes the pressure of the cost of food and the making of food off of you.
Of course as someone who has hosted dinners like this I can tell you that it's a gigantic problem when everyone comes with a million dishes that they expect they can pop into the oven and there's no room in the oven, how do you keep all the food warm?
So your next best bet would be to find a restaurant that delivers, and everyone splits the bill making sure you get the money up front before the day, don't wait for them to send it to you later, or, go out. Find a place that's open and just go there.
Or better yet, just don't have that many people over.
It might just be that you don't spend enough time with them but you said you don't really like the additional six people that are coming that you don't have much in common with them and you don't have much to talk with them about, true you won't get much time to do small talk with them if you're going to be hosting, but still. Not a great situation.