Are you familiar with Alexander's Lodge? (https://alexanderslodge.com/) It looks like they have a couple of Tesla Destination Chargers, which typically work at around 40mph, (40 miles of range for each hour of charge) so it would work to drive there, charge for an hour or two, and have enough range to comfortably drive back to Portland in a day or two.
Of course, that doesn't mean the Model 3 is right for you in every way, but it's interesting to think through scenarios like this.
The ideal (for me anyway) would really be to have a supercharger (or other fast charging) at Sunrise, and ideally one in Packwood as well. Or forgot the whole enterprise altogether and put in a bus service like Zion has.
Of course, Rainier is only one example. Once you get into Eastern Oregon, the charging situation is even worse.
I would hope that if we get a more forward-thinking government in the next few years that we start thinking about this kind of stuff, because thinking about the carbon impact of "enjoying nature" is pretty bleak stuff. I'm actually interested in this problem enough that I've started to look at the economics of building charging stations (demand charges!)