Good luck Claire!
It looks like you'll have plenty of sun and lots of room there. I'm envious! But it might take a lot of time and work once several families start to depend on you.
And thanks for posting. I hope you keep letting us know how your CSA project is progressing.
Most vegetables, I would start in 72-cell trays or even 50-cell trays. (I don;t have room to pot-up, and try to transplant directly from the cells into the soil. Maybe lettuce does well in a tray as small as you mentioned. But I'm not very experienced with starting large numbers of vegetable seeds.
I think of Sweden as being "far North" and cold, but does the Gulf of Bothnia moderate your weather? I'm just curious: when is your average first-frost-date?