Having found out on a few occasions what peroxide feels like in the eyes from a few silly moments involving contact lens fitting.. I would buy a wee garden sprayer with bike wash scribbled on the side and fill it up.
Just carry it in the side pouch of a camelbak and be more than happy to give them the bike but insisting you clean off the dog muck on the tires before stealing it. Then maybe grin and ask if they want a wee scrub too.. squirting one of them in the eyes,followed by the others. Just make sure the nozzle is always set on full pelt and not on a lame mist.