You actually have two good options on that trip to refuel with water. One is the creek at Jones Hole near the end of Whirlpool Canyon. This creek runs reliably high and clear all season, but would require iodine or bleach obviously.
Or you can just fill up at Echo Park. They have a spigot there for public use.
Side hike up Winnie's Grotto on river right immediately after the rapid, and then Jones Hole of course. JH has great rock art in the deluge shelter, and the waterfall is worth going to because you can have people block it up with their behinds up high, let it build and build, then come crashing down on whoever is standing below. Tons of fun.
Hope you have a fantastic trip! I was on there two weeks ago and it was incredible, the bugs weren't even that bad!