I have a reservation for 3 at 8 pm, today the 8th. Would it be a problem changing that to 4 people? Thank you David Silva

You should contact the restaurant directly regarding your reservation for a prompt response. In my opinion, it may be a problem since it's Friday night and it may be busy. Better to talk to them ASAP than to wait at the restaurant for a bigger table. Cheers!

No cause you can always seat 4 people in a table.