Concierge/Guide in Lisbon

I was in Lisbon last October and stayed at the following three star hotel in the Baixa neighborhood of Lisbon.

Be Poet Baixa Hotel

I really liked the place and they get high reviews on booking.com. Location was central and great

You might try contacting management and ask about 10 rooms or just go to the website. Or go through booking.com

They do have a small restaurant. Breakfast was very good.

Again, I would contact management and ask about a private celebration.

If Be Poet can not accommodate you, they might be able to make recommendations.

Off hand, I would say look to see what big name hotels are in the area you are interested in staying. Something like one of the IHG Hotels (Holiday Inn, Express, and Intercontinental all are in Lisbon), or the Hilton, NL, or Radisson chain.

First, they will be big enough to have the rooms, second, they have event rooms, third, they have a staff large enough to arrange a small event like this. I would opt first for a place with an onsite restaurant, something more than a bar or breakfast room, if that fails, then inquire about catering in, or reservations at a suitable restaurant.

You could probably filter a list of a dozen hotels pretty quick. Smaller hotels may be able to do it, but the task would be a bit much for most, many also do not like large groups, a "too many eggs in one basket" type thing, you cancelling (things happen) would sink them. Maybe some on here know of hotels used by Rick Steves tours, those might be an option.

As for someone local, not much help there. I did run across this person: https://juliedawnfox.com/ when doing some research on Lisbon. Can't vouch for them, know nothing about them, but they do advertise consulting and itinerary services.