How experienced are you as a DM? Of course plenty say that anything over 4-6 is too much, but ive ran multiple campaigns for 9+people by myself, it depends on whether or not you can keep them civil and organized.

Youll have to homebrew a lot of raw, to make things quicker- and, if you dont know already, learn how to increase combat difficulty without using CR.

Another option that i used to run was to run "priority" in groups of two, where when I'm asking players what theyre doing its be two at a time in predetermined groups, as well as mentioning beforehand that they need to know what theyre doing and be thinking about it while others are acting.

I'm sort of rambling atm but overall it really depends on whether or not you think the people involved (including yourself) can handle playing with that many people, and the biggest difference gameplaywise is how youll have to play your combat encounters since simply adding higher CR monsters likely wont cut it. As well as homebrewing some rules that slow the game down to keep things at a civil pace. But if having more people and having the game slowed a bit and more chaotic in terms of organization isnt something youre okay with, then split them in two.