When I was there last year for the eruptions, I only had my 28-200 with me and found it worked well enough. I needed to crop via APSC mode a few times, but if you're bringing a TC it should be a non-issue. Other than the viewpoint for the eruptions, I don't think I shot over 70mm though.
If photographing the eruption at night, I HIGHLY recommend going as late as possible at night while they are still open. It gets very crowded when it first gets dark, and it was hard to find space to set up a tripod without it getting bumped by people. Also, it was very misty at the park even though the rest of the island was dry, at least when I was there.