I have started seeds in all kinds of conditions and seem to learn alot about it from expeience! The number one biggest mistake is not covering your seed planters with a plastic or glass cover till the seeds sprout! The reason is most soils contain peat and when it dries out the seeds cannot break through the surface. I woul say the second problem is wetting the seeds too much before they sprout which can cause them to rot or damp off! Temp is ver important for seeds like tomatoes and peppers! The soil should be above 55 or even 60 to have them emerge successfully!.
If you lack room after the seeds sprout the cole crops can be put in a cooler area without any problems I don't like peat pots I stick with plastic or styrofoam containers! I started putting leaves or paper at the bottom o all myseed planting boxes and it seems to hold the moisture nicely after the seeds sprout!. If you want to sell your plants get the flats with 48 up to 72 cubes per flat Agway has the 72 flats for only 69 cents!
After seeds sprout get them into good light or they will be very thin and leggy with poor health! When planting small seeds cover the seeds with potting soil that you finely strain as you top apply it to take out the big pieces! Never put your new seedlings in direct sunlight but start off in a partly shadded area for a few days! Cold frames are also a nice place to put some early seedlings where the temp does not freeze them!
Try digging out a raised bed about a foot deep and use it for your new seedlings like a covered cold frame and replace the dirt later in the spring back to the raised bed again! This way you can referbish you raised bed dirt with a few added soils while using it for a early season seedling starter!!