What are some dining options in Boston Massachusetts for a group of 20 that are a little loud, nothing crazy fancy?

Try the zoo since the animals don't care about loud noises.

Once upon a time, a little girl named Pickle Sauce bought a house deep in the woods. As she skipped to her loo, she tripped in the weeds and was promptly eaten by a wolf. 

you’ll need a reservation wherever you go. Try Beerworks Fenway, melting pot, fire and ice

Summer Shack at Alewife, Bertucci's (numerous locations). Look for other options on OpenTable or Cheap Eats (Boston).

Do not go to these sites. They will steal your credit card information.

The Hot Pot in the financial district near South Station

j

Durgin Park has a dining room upstairs that would handle that. It's not super expensive, and old Yankee food. Alongside Faneuil Marketplace, right near a parking garage and near enough to the T.

There are endless options based on that criteria.

In downtown Boston or a suburb? Section of Boston? I.e. Back Bay, North End, Mattapan, Roxbury...?

Cuisine? Pizza? Seafood?......?

There are numerous "pub like" restaurant/bars in the greater Boston area that might work?

http://www.theemeraldrose.com/index.html

https://www.theirishcottagepub.com/home

If you're on the south shore I wouldn't drive the Methuen.

Chuck E Cheese.