Mission Chinese with group
The largest group I've gone with was about 6. You can certainly try to call them for a reservation, which I haven't had much success with. Best bet: go for an early dinner (~5:30PM) and they might be able to fit your group at the communal table.
If you're more risk averse, I'd recommend Legend in Chelsea, especially with a larger group. They have an entire downstairs that's suitable for banquet-style dining and they take reservations. The food is some of the better Sichuan I've found in the city, too.
La Vie in Szechuan or Cafe China in midtown are good options, but they're not the same as Mission Chinese, which is kind of a class unto itself.
My recommendation would be to do takeout from Mission Chinese. If you aren't staying nearby, there are a lot of bars nearby that don't serve their own food that will happily let you bring food in if you get beer.