Depends on what size plant you are talking about tbh
It's fine when they have one set of proper leaves.
Not fine later on when they are all in three inch pots
And then....
.... so I would germinate them indoors and save the cost of a propagator, and then section off part of the greenhouse to heat once they are too large to keep indoors.
and make sure I use foil on the room-side of the plants to reflect light onto them to try to stop them getting leggy
