I just responded to your other post and told you to walk them together and now I read this...hum, I walk 3 dogs at one time. Its not always easy, but they love going together. I find the most important thing is to feel confident in your equipment first and foremost.
First, its important that you have a collar that you are 100% sure will not slip off. I have found these collars similar to choke collars that only get tighter when they pull. They are called "Lupine Combo Collars"
LupineŽ - Medium Dog Products. I love this collar--you feel so safe with it. 2nd, get really great leashes that give you good control...I have found a 6 foot leather leash is best. Avoid the thin retractile leashes. Next, hold the leash with your thumb looped over the handle. It gives you even more control and makes it impossible for the dog to pull out of your hand. I can hold my two "pullers" with one hand and my "good dog" with my left hand.
Watch your reaction when you see an "obstacle" approaching. Dogs can sense our apprehension. I tell my dogs "Leave it" when I see a bike coming or another dog coming. This helps. I also try walking a little faster saying "let's walk" so that we can get past the obstacle quickly. I don't stop walking when they start barking or lunging. I just keep the pace or pick it up a bit. I am not sure stopping to "sit" would help in my situation. I also do not invite other dogs to sniff or say hello when I have all three of mine out together. Its just too much.
The type of collar I mentioned above also allows me to give a little "jerk" to get the dog's attention if needed. Also, with the leather leash, its easy to bring them in closer to me if I need to. You could do that when you see a biker coming. Remember too that you have a foot--you can use your foot to
touch your dog's back side--(
NOT KICK) just to get the dog's attention back to the walk when its out of control and you have your hands full.
I wish there was a magic way to do it (an easy button). All dogs are different and all environments are different. I definitely would not give up walking the dogs at the same time. Keep working on it. Try to find a route with the least amount of distractions. You sound like you are doing many of the right things already. Maybe others will offer more suggestions to you.