This is something you should be able to determine yourself.

Consider how much room each place will require, and how much clearance is needed between the table and the wall.

Also consider the shape of the table.

The ideal distance for dining table clearance is 4ft for people to come and go from the table comfortably. So this should allow you to have a 4 ft X 8ft table, large enough for 8 people.

Breakfast room and dining room are sort of different animals ..in order to do them together it may be better to do a smaller table that expands for special gatherings...and fitting 8 people should be possible if you choose a table with the right dimensions for the room...keeping in mind the room needed when table is full that you still need room to walk around the table...also any side tables needed when entertaining...