Tamarind Tree has the capacity, the food, the ambiance, and the prices to help you.
The bar is good, too, if a little stingy. The Tamarintini is nothing, but Kumquat Crush rules, unless the orange ones are out of season.
If you can get a local guide, do so, as the menu is very uneven.
They have a great presentation of Bo Bai Mon, on those few occasions where the "everybody-is-tripping-over-everybody and-nobody-knows-what's-going-on" staff can hold their coordination together well enough to get the food to you while it is still hot... Other TT hits - coconut gelatin (get it early, with the apps), Tamarind Tree fresh rolls, Pickled Bon Bon Salad, Mango Salad, ice cream (Tham makes it there - get them all). Their bowl of green greens is delightfully green, but otherwise inscrutible. It needs a spash of vinegar. I recommend you explore the menu by trial, as the descriptions can sometimes mislead.
Get coconut juice drink, too.
Green Leaf is even better, IMHO, but a visit to be sure they can seat all of you is a good idea, as their seating is limited.
I really like Dragonfish which is at 722 Pine in the Paramount Hotel. (Apparently there's one in Portland, too.) It's Asian fusion which I generally think is dull-dull-dull but this is REALLY tasty. They have some nice round tables that would be good for a group your size and the menu is set up for ordering lost of different things and trying some of everything.