They won't take up much room on a coffee filter, in a baggie. Pot them up after they germinate.
They might well still be small at the end of summer. But if they're still in small pots, couldn't they over-winter in the greenhouse?
If you get a LOT of germination, put several of them into some pot as if they were "flats".
That way, if 75% of them die, you still have several in that pot.
If I BUY a plant, I feel like I'm just growing someone else's plant for them.
If I start it from seed, it is MY plant.
But, really, I'm just cheap.