Hi, it is a bit riskier to walk more than one dog at a time because if anything happens you are kind of limited to how you can physically control them. One dog you can put your hands on. Two dogs you kind of have to be just pulling leashes unless you manage to let one off. Same with tight spaces or sidewalks. Plus 2 dogs are stronger than 1 and they can tangle the leashes up in the middle of the action. You also have to be aware of 2 dogs and their surroundings while picking up poop. Once we got “attacked” by one of those small white dogs that was leashless. And now both my dogs really dislike small white dogs, as opposed to only one.
That said I still walk 2 at a time, one on the right, one on the left on a semi-relaxed heel. Left hand holds both leashes and the filled up poop bags. Right hand is free for a quick tug on one leash or another if needed. I let them have fun and do dog things in 2 or 3 spots in the walk.
Sometimes I use 30 foot training leashes and wind them up on my left arm for the walk, leaving about the same amount you would get with a 6 footer. Then on specific spots I unwind them and the get to walk and explore like a pack. Then wind back the leashes and we go back to heel. They do need to understand that those are different “modes” so that it does not spoil the heel.
You kind of need both to be already reasonable walkers or it is too much frustration for you and the dogs. Like if you are correcting dog #1 with about turns or stops it is not fair for dog #2.