You're not asking for much are you.
Ultimately, I prefer leash walking two. Do three all the time and have done 4 and 5 on many occasions. I think the key is the work you do individually though. Depending on what kind of training is going, where the dogs are at, what issues may be going on - it's not unusual for me to take each dog out solo.
Ideally, Bob and I walk together. When we had 4, he'd take 2, I take 2. Now he takes the husky and I take the 2 big boys, and we mix that up sometimes too but that's pretty much the norm.
My Siberian husky has an ability to add an unruliness to a leashed pack walk. While older and has nowhere near the physical or energetic capacity of the younger ones, he's truly the patriarch of my pack. If he's feeling extra spunky and goofy, it has a way of trickling through the other two. He's brought in line quickly and peace is restored but it can make for a bit of pulling when otherwise there would have been none.
Off leash, when they're younger, they love to explore and that 50 feet can turn into 100 in a matter of seconds. I don't think it's anything to do with them disobeying, it's just so darn interesting out there and they do need to be reminded about "not too far".
For us, it's not a recall, simply a distance command. My boys pretty much stop dead in their tracks and kind of hang out until I get a little closer. You may seem like a broken record at first, but as they get older, the distractions become less and the distance becomes clearer.
It's also a lot about them wanting to be with you. Off leash for us is more of an exploration walk, not really a purpose walk. When they're interested in smells, I stop with them, give them a chance to explore that area, do a little marking, ask for a few commands for a few treats and we head off.
With the "not too far", I also mix it up a lot. They'll be stopped up ahead and I may do a complete 180, or turn and head off to the left or right. I don't recall them, it's up to them to pay attention to me. This randomness of directions has them keeping their eyes on me to see which way we're headed.
It sounds like you're walking, off leash, with a purpose - to get to the ski area. Purpose walks for me are always on leash. It's sometimes different with just my shepherd but he sticks to me like glue. The three of them together, I want full control of all their actions if we're in a more populated area where there are going to be various human/dog encounters.
My boys are never allowed to interact with random dogs on trails, well not in the way most people allow them to sniff each other. They're recalled and stay with me. That physical contact is not necessary in my books. They can smell the other dogs from a distance.
It may sound oxy-moronic but my most important socialization is teaching my dogs to ignore other dogs. Unless they're in our yard or we head out with specific dogs, they're treated pretty much like wildlife or livestock - you don't go anywhere near them.
As well, choice of venue is important to me. Some of these trails can be as bad as dog parks, even worse, with owners' lack of control and letting the dog run "free". We avoid them like the plague.
I think off leash will always have its challenges. To me, the pack work you do with the dogs, in all situations - in the house, in the yard, fenced in areas or in the open wilderness, and the reinforcement of trained commands - recall and loose leash, by my side walking being the most important - has the biggest impact.