Rosemummy, 1) Seeds do not need strong compost, mix some fine compost with grit and washed sand about one third of each, sow the seed, always read the packet some seeds need to be deep some barely covered, water from the bottom and they need warmth a window sill or greenhouse. 2) like babies they need weaning, you cannot put them onto rich compost, as soon as they show two proper leaves move them on, a mix of half compost half sand and grit, when they have a true leafy top then pot them on into larger pots of compost with some sand and grit. 3) harden off the plants, put them out during the day cover at night for a couple of weeks then plant out.
I know you are a busy lady but seeds and seedlings need attention you cannot leave them or they are gone. The best way for you would be to sow just enough in a pot so you can get it on a window sill then prick out as soon as the two true leaves show, keep watering from the bottom (stand in a dish until the top shows damp) over watering will kill anything except pond weeds. Little and often is better than a lot and no time to prick out or pot on, a waste of time and money, it is OK for us old retired lads we have time some people do not, so cut your coat as they say up here.