Originally Posted by PentHassyKon 
Just to clarify - these are shots that I envision taking inside my children's auditiorium or stadium while they are playing with either their marching band, symphonic/orchestra, or jazz band.
Ah, marching band - that's a unique case. Large area and you *can* get close to the actio when they are on the opposite side of the field. However, those venues tend to be pretty well lit. I wouldn't rule out the 55-300 for that, actually.
My experience with venues large enough to require 200mmor more is that they are *often* brightly lit enough to be able to get by with a slow (eg, f/5.6) zoom. Indoors or out, actually.
I do also have an off brand (gold star, IIRC) A 135 2.8. I have not tried using this yet since I've been focusing on their outdoor venues and the 135 is not long enough.
True, but it will be your best friend in the school auditoriums and other indoor settings. Too long for small nightclubs, actually, but nice for most small-medium auditoriums (and remember, cropping is still legal!). If it's an especially large venue and you're toward the back, 135 won't be long enough even with cropping, but then as I said, venues that big almost always have enough light that you could use your 70-210 or even a 55-300.
Keep in mind that I don't have press credentials
I've only had that kind of access once myself. But still, it's usually not difficult in most venues to walk toward the stage, shoot for a while, then return to your seat. People do it all the time, even in major concert venues. Beats the heck out of trying to point a 300/2.8 at the stage from the 75th row without knocking out the people in the row in front of you.