TheFork users who ate in Trento have said really good things about Patelli, Tipico and Il Simposio. Maybe you should give them a try!
Some of the more popular KM 0 - Chilometro zero restaurants well suited for group dining in Trento according to TheFork users include:
Patelli, with a 9.3 rating
Tipico, with a 9.2 rating
Ristorante Lago Park Molveno, with a 9.2 rating