In reply to TMM:
You can put them in a very thin plastic bag if water is a concern. Your bigger consideration is the battery life, you'll either need a serious battery or ability to run while plugged onto a power bank, to keep it cranking out the choons at sufficient decibels needed for a group who may be spaced out when you get to the pinnacle section.
Factor in some weather and wind on the ridge and the need to compete with background noise and overpower the constant noise of other walkers shouting angry obscenities at you -- you'll need some serious decibels.
Perhaps an "ICE" system from a car, there's a lot of cars my way have been able to solve the background noise problem with sufficient amplification (in their case defective exhaust and car backfiring every time the throttle is suddenly lifted) You will need a similar approach for enjoying the unspoiled outdoors.
I suggest an ICE system with a dedicated amp for the bass tube, pair with a couple of high capacity car batteries, which you team can take turns to carry.
Sorted...
Post edited at 12:19