How exciting that you will have a greenhouse!

The tomato temperature question you might want to ask on the tomato forum, but here is what Johnny's (seed company) says about tomatoes:
"Grow seedlings at 60-70ðF (16-21ðC). Water only enough to keep the mix from drying."
"...avoid setting out unprotected plants until night temperatures are over 45ðF."
So that should give you best growth temperature and minimum temperature for young plants. They also warn about starting too early and getting plants that are too tall and blooming.

Do you have heat in the greenhouse? Here in the NE it is difficult to have a greenhouse without supplemental heat unless it is only used as a season extender at the beginning and/or end of the growing season.

The greenhouse will have heat!! So excited. I cross posted the question to a few related forums but it is always good to get info from my neighbors.