I'm planning a grow with a similar medium, 2 parts peat moss 1 part perlite and 1 part vermiculite, I'll be using GH 3 part flora starting off at the end of week one or so with very diluted nutes (1/4 strength or less) every second watering then slowly moving up
Your seedling should have enough nutrients to keep itself going for the first week but since peat moss/perlite don't have any natural nutrients you will have to start feeding sooner than you would with organic potting soil