I'm fortunate that the buses for all three schools stop outside my house however I believe one of the conditions of bus use now around here is that those Grade 3 or younger must have an adult to meet them/wait with them for collection. So even if mine were small still, I would need to dress the day care kids and have us all at the end of the driveway!
Other providers have a wagon which they put their little ones in to go and meet the older school-age children. I love my wagon and I think for the most part that works well until the cold/wet weather comes. I don't know if it's possible to get covers for them to keep little ones out of the rain, snow, and wind. There are days we only go into the yard because the wagon isn't practical for further afield if there's unplowed snow.
A multi-stroller might suit you with a wind-rain cover. It's the wind that is biting when sitting still as a smaller child in a stroller would be. 10 mins to the school/bus stop, a few mins hanging around waiting for your child and 10 mins back again might be really hard come February.
Another couple of suggestions..could a parent in your community who is meeting their own child also pick-up/drop yours so you can avoid the transportation issue? Is there an older child at the top end of the school who might escort yours to and from for a bit of pocket money? Even if this could be arranged over the Winter months that might make life easier.