I use peat and compost mixed, which seems to work fine so your mix seems good too.
One thing I've learned is to make the mix the right consistency, not too wet so it is a muddy mess and not too dry so it crumbles, but just right so it hold its ball shape while tying plants. More peat helps the ball hold together. I use some kind of sheet moss to hold the whole thing together (with string as well).
Good luck can't wait to see how they come out!