It's hard when you have a group of really young ones and I've just gone through that for a few months with 3 children under age 2. However, as soon as children are walking well at about 18 months, especially if they are a larger sized child, not a teeny little thing, I start them walking beside the stroller for practice up and down the sidewalk. I have the 'toddler restraint systems' that I bought at Walmart with ponies and puppies and an Elmo that I put on them and attach with the string (not leash!) to my wrist.

I have a 22 month old who is already so great at this with just a few months of practice that we can travel huge distances again with just my double stroller again. Pulling my wagon and trailer with 3 heavy babies hurts my shoulders or pushing my triple stroller hurts my back so the quicker they can walk the better.