don't think you're one of them. You seem to be insightful, pragmatic, and smart.
So, what kind of radiation mask is it? When I did a round of stereotactic radiation (they immobilize you, then shoot two concentrated beams at the target (which was in my lungs). I was hoping I could quickly find a picture of me in mine, but my iPhone's all screwed up.
Basically, though, what they did for me the first day is they lay some mesh in water (about 140 degrees celsius - just kidding, fahrenheit - kind of warm bath water) and then they lay it on your face and shape it. As it cools, it hardens, and you end up with some kind of thing you could decorate for halloween - cross between football mesh and Eddie from Elm Street.
The next time in, you reuse it, they strap you in. If this is what happens in your case, don't be afraid to speak up if it's really not comfortable. 'cause you'll be in it for 40 mins (in my case, at least the first time) and immobilized, and then it becomes hard to complain.
In my case, they also had a little background music on a multi-disc CD player, but it was really so I could hear it, not them, and unfortunately they had it set to something like "sample every track for 5 seconds". We'd have 5 seconds of cajun (yay!), 5 seconds of blues (yay!) 5 seconds of Tyler Swift (errr....), 5 seconds of Aerosmith, 5 second of James Taylor (okay) and then get buried into 5 seconds of Butthole Surfers or something (which is actually okay, but you get the point, and 5 seconds of anything is either too long or not long enough). By the time we were 15 minutes into doing it over and over, I realized how this was happening and couldn't really say anything. I mean, you can say things like "help" or "stop" or "yes" or "not", but usually it's not an involved explanation of how their CD player is on sample mode and it's driving me nuts.
It also physically hurt, so next I made a point to describe - while they were applying the mask - what they had to tighten or loosen to make me comfortable. All remaining sessions (maybe 5?) were comfortable after that, and I bought in my own CD of music so I wouldn't be stuck listening to their stuff
So, if it's similar, there might be some starting pains, but after I took care of the uncomfortableness and the music problem, I actually started looking forward to it as relaxing, particularly with my choice of music.
Hope the radiation and chemo work just fine. In your case, once you take out the tongue there's no putting it back, so that sounds like a worst-case / last-option scenario. It sounds like you're right to take the chemo/rad first.
Good luck and tell us how it goes!