I have led a couple tours with Virtual Pioneers in the absence of our fearless leaders but mostly served as support personnel as we went across builds in Second Life on Sunday evenings.
One Sunday last summer, I found myself with a large group of newcomers to Second Life. The tour went across a wide area and took us out of chat range. I was able to get everyone on to our group chat and use a technique Esme from the ISTE Tour group often practiced which was to place a group call. This then allowed us to navigate together on voice or text.
I still prefer text chat as a participant and would like to always offer notecards with landmarks and additional information. I think this is helpful if there are latecomers and also to those who have bandwidth issues. I have found that if voice is used, I like the sound to be run through an IP address/ land stream so that it can be easily clicked on using the music controls through the viewer. Having had experience with managing an art gallery and assisting with djing in SL, I am somewhat familiar with this and stream rental makes sound optimal for users - especially newcomers.