Yeah... I do all that. Basically, I just try the high section, and see what is comfortable (or controllable, at least!) and go from there.

Overall, last couple of years I have started to take everything down a half-step or so, to adjust for my aging vocal chords. It's easy enough when I'm solo (just transpose the entire arranger down a half step for the whole night), but it's a PITA for any guitarists working with me!