I have the same concern. I work on commercial garage doors and everything is extremely heavy. I usually use my whole body to lift things like sections,
openers, springs etc. Avg weight of the parts I lift are around 100-200lbs. Heck my ladder that I have to take off at every job is 75lbs.
I had a hard time before, don't know if I will be able to lift that stuff now.
Not to mention working outside in the heat no bathrooms a lot of the time. I'm worried about
the bag getting to heavy and sweaty and coming off.
As far as your situation all I can say is make sure you have plenty of liquids on hand to keep you hydrated. Do you have one of those little fans that mount above your head? I have seen some buses with them. Maybe you can point it toward your ostomy to keep it cooler?
Oh and if you are concerned with output, maybe you can pull over between trips when there are no kids on the bus and empty it in a container that you can seccure really tight and then hide it somewhere. Maybe a backpack or something. Also pack some baby wipes. Just an idea.