How old and how many children do you have?
I can sympathise as my two oldest, especially my 4yo, like running ahead. Dd1(6) is fine, stays on the inside of the oath, stops at the one road we have to cross. Ds1(4) frequently runs ahead too far, balances along the kerb, jumps in the puddles in the gutter etc. dts(2) are only allowed to walk on reins as they want to stop and pick every leaf, every stone, puddle jump. While dts will hold my hand nicely, at his own request, his sister refuses. But is happy in reins as it gives her the freedom she wants, while I know she's not going to end up flattened by a car.
Ds1 is told every time he can run to X, and if he goes too far he has to hold my hand until the next run point (we've agreed these in advance and remind them before we go). If he continues I carry a spare pair of reins and he gets one warning that next time means he goes on the reins. I have followed through on 2 occasions. Showing him I've got them is usually enough of a reminder so I don't have to hold his hand more than once.
As for all the bags. Using today as an example, I had 2 book bags for the older two, two back packs and two lunch bags for the younger two. Dd1 carries her own bag. Ds1 is currently slightly too small and his book bag drags along the floor - I had to replace it due to tearing the bottom off by the end of his second week in school!
So I have a buggy buddy which I used to use when we put the twins in their pushchair. It's great for clipping all the bags on and has a nice padded grip to hold. I used to get the big two to put the twins backpacks on and the twins lunch and are backpacks. But it became too much faffing then carrying the backpacks and lunch bags after the big two had gone in to school, as well as keeping hold of the twins' reins.