I have never tried TT at RFC. I did not know they even served it.
Kona Cafe (at the Polynesian) has the TT everyone knows.
They also serve a TT in the Poly counter service area (Captain Cook's?

) However TT is much better in Kona Cafe. (The difference of a chef and a short order cook.)
And yes, get an ADR. Kona is a good place to eat. You will not be disappointed.