How large is your greenhouse?
If it is too small, it will heat and cool too fast and not work as well.
I would add a little compost to your seedling mix, not a lot.
It was impossible for me to be totally organic here, so I do as well as I can, the best seed starter that I have used, is Walmarts Pro-mix potting soil /mix.
It makes the seed jump up and start right off, excellent starting material.
If you need more heat, consider those large soda and juice or milk bottles filled with water, the sun will warm them in the day time and they will release the heat as they cool, I have used barrels of water, with the seedlings on top of them in my greenhouses, for years.
I also sit a few bottles of water in with the young plants when I plant them out.
Don’t let the water collect in the seedling pots and rot the seeds. At night you can lay plastic over the top of the pots and take it off with the first sign of moisture collecting on it.
It is best to water from the bottom, or do as I learned to do, I use mostly styrofoam coffee cups to start seeds in, poke 3 small holes in the bottom, but when I plant, I leave a small area free of seed and put a mark on the lip, so I know where to water.
Like posting, a few is never enough, so there was no way of knowing where to water if I felt the need to pour it in the pot.
And you can write with a good ball point pen on the cup.
I always gathered up the used cups at meetings and rarely had to buy new ones, as they are usable for about 3 years.
Sun, heat and water and you will do fine.
On the small seeds, just barely cover them, 1/8 to 1/4 of an inch of soil on top, not as deep as you would outdoors.
Good luck and have fun.
We have posted cheese making several times, Tenth Amendment Champion, did a good one in December or about then, with photos, as my memory recalls.
Like planting seeds, it is easy, once you learn the tricks of it.
Hold out for your goats, they will laugh at you, my love of goats goes back to a rank billy goat, that I considered my friend, when I was only 3 or 4 years old.
I remember bringing him in the house, we were both looking at ourselves in the tilt mirror on the dresser, when all hell broke loose, my mother had found us and she did not like goats, and LOL, not in her bedroom.......
I asked my aunts several times and could never get them to stop laughing and tell me the rest of the story......I fear the billy goat attacked the mirror to get at the other goat.
~boing~ I should have had a V-8. Why didn't I think of that?!? LOL Good thing I posted that question!
I'm about 50 miles from a WalMart so I will have to wait until I make it to town to get some of that Pro-mix. But, I will keep it in mind.
I am like you with the water bottles. The first time I saw those wall-o-water ads I figured I could rig something up and have been saving almost ALL containers since then. And since we are in an area where we are either feast or famine on rainfall I actually go out in the rain sometimes and fill up empty bottles from overflowing rain barrels so as not to let the barrels overflow and to save as much rainwater as possible.
Last year those water bottles saved my tomatoes and peppers when we had a late freeze. I can't explain it but I'm one of those people who always think I can get by with putting out my plants a little too early. Most years my gallon milk jugs of hot water actually save the plants though. When I know we are having a really cold night I will actually fill them with very hot tap water around dusk so they'll keep that heat as long as possible. And like WCG posted a moment ago, it seems that if we have those cold nights in spring they are typically followed by a warm day so no harm done. So, of course, each year I end up putting things out early... LOL
I was also able to make space to actually move around and be seated inside the house by carrying my wintering-over potted plants to the greenhouse. I'm thinking the man of the house is glad he bought me the greenhouse for that reason also.