it might be easier on you to work with one solely for now and then when that one is going good then take on another one and so forth. I have four horses and I know with me training three of them it can be very time consuming and since this is your first go around on training a horse.
I would have to agree with this one. These horses are so young that they really need small daily training. I worked with my gelding 15-20 min a day or twice a day, on basic manners and groundwork for months before I could do more complicated things. It has helped IMMENSELY! It takes a lot of energy and time to train a young horse. Trust me, I'm green on green too (not by choice). It is hard to learn a new language at the same time you are teaching it.
Check out the new thread about groundwork. A lot of great advice there. Respecting space is definitely where to start. That is the bases for a learning relationship. Without that you aren't going to be able to teach them anything because they won't respect you.
I also second the idea of sacking out. After you have established yourself as the leader (which they will test), sack them out to the world. Take them for walks, bring them to everything you can. Tractors, cars, trucks, fences, animals, leaves, whatever they might spook at. It will make a BIG difference in their training.
Its your first time training so take it slow, it is easier to train a horse into a bad habit than a good one..don't ask me why? They drive me crazy like that....
Good luck and stay safe. You might want to wear a helmet even if you are just doing groundwork with these horses. I knew someone who was almost killed just grooming a baby who reacted to quickly.