Restaurant for large group in Bologna

No idea- been to Bologna but don't know it well enough.
Another possible resource could be contacting the various food tour companies- there are many in Bologna and see if they have recommendations (but you may have already thought of that !)

To add to Christine's useful suggestion, you might also contact the "Bologna Welcome" visitors office?

https://www.bolognawelcome.com/en/information/contacts-eng

30 people is not a so large group. Almost every restaurant can accommodate you for a dinner, but you must book it in advance. Probably only few very exclusive restaurants cannot accommodate 30 people. You can choose depending by the kind of restaurant (Emiliano, Italian, international, pizzeria....), the position in the city (close to the central square, in the historical part, in the countryside, in the fair district....), the cost (low budget, high budget....). In any case usually you must choose the same menu for the whole group.

Try Donatello. Bolognese cuisine.
Book in advance.

https://maps.app.goo.gl/2ehBZWCCGUdvMKH3A?g_st=ic

Thanks for the suggestions!
Roberto, that looks like a possibility.
ricky what might you suggest for an Emiliano restaurant in the center of Bologna, cost perhaps 40-50€ per person?

I was going to suggest Ristorante Diana however, it's been a few years since I dined there and trying to recall if they'd be willing to designate a chunk of their dining space for a single-party.