For posterity... I ended up keeping the repeater boxed up this year.
Most folks brought 4W or 5W handhelds with upgraded antennas. VHF coverage was excellent, with strong reception (S9) from the center of camp out to the main gate and waterfall. Coverage would drop a bit (S5-7) further up-trail at the second waterfall, but was still intelligible.
There was effectively no coverage once you reached pavement, and it definitely wouldn't have reached Paulina Lake. But we are within range of several area repeaters, so that might be a good backup for infrequent uses like this.
Using a rubber-duck style antenna was considerably worse. S5 from center camp to the waterfall, though still usable within camp.
The takeaway here: Upgrade your antenna. (More on that below.)
In the future, if we don't use a repeater, it would probably be a good idea to pick a frequency within the simplex range of the band plan. Not that we had any interference (in fact, we didn't even need a PL tone this year), but if nothing else it would let the fancy radios auto-configure themselves properly.
Also, a few spots in camp could actually pick up NOAA WX radio broadcasts via HT this year, which was useful when the clouds looked scary. It was very much location dependent, and didn't work by the end of camp. Just an interesting observation.
More on antennas this year...
The Nagoya NA-771 was popular for folks using the Chinese radios (Baofeng/Wouxun), though apparently it can put stress on the RP-SMA connector's solder joints due to the radio's design. We had one potential issue manifest due to this.
@WoofyTheBunny (K9BUN) recommended the Diamond SRH77CA instead. Apparently it's designed specifically for these radios and has a strategically placed piece of rubber for strain relief.
If you're using a Japanese radio, you'll need to find something equivalent using a normal SMA connector instead of RP-SMA. I used an Icom FA-S270E antenna and was happy with it.