The "new rules" aren't in affect yet, as far as I know.
Looks like the official adoption date was May 18th and the publication date was the following day. So 90 days is just a few weeks away. At this point in time, I would suggest that any debate over two watts vs. a half watt under FRS rules is almost nonsensical and completely unproductive.
As far as the OP's situation, the real issue is that of a "grandfathered" licensee who most likely never bothered to renew the license. If memory serves, failure to renew would clearly negate the grandfathered status once and for all. If they're using low power gear (2 watts or less) they're only a couple of weeks away from being legal. If they're using higher powered portables or mobiles or base radios, they're clearly operating illegally, regardless.
If I was the OP, I'd be reminding the camp that their grandfathered status holds only if the license has been properly renewed and is not expired at this time. The second thing I would remind them of is the fact that FCC rules clearly require users to share the frequencies and that there is no guarantee of a private channel, even under the old rules way back when they were first licensed. If their license is valid, they are obligated to play nice in the sandbox. If their license expired, then they are no longer grandfathered, and the lower power FRS rules would apply. I think it would be a waste of time to try to explain today's rules which will be obsolete in less than 30 days so I'd just mention the new rules that will be effective in August. If they complied with the new rules now, it would probably eliminate most of the interference to the repeater, but they'd still be stuck with hearing the repeater unless they figured out how to enable PL. Then the big question would be what radios they have. If they're bubble pack, that is easily fixed at no cost. If they're commercial grade stuff, then there's a visit from a radio tech needed and that costs money which it's unlikely that the Salvation Army would pony up give the fact that they most likely haven't spent the buck to keep their grandfathered license current.