Well, that depends if your compost heap has been composting properly or if it still has the stinky anaerobic stuff going on. You can tell by the smell. If it's compost, it will smell like wonderful healthy soil. Your plants will jump up and be bright and beautiful growing in that.
Since it's getting late to be starting seeds (hot, dry weather is not easy on seedlings) I'd go for some transplants of the plants you already have going.
