The value in the individual guide is to avoid the line??
No. As acraven said, what a personal guide does is impart information. You can skip the long ticket lines with pre-purchased tickets or tours offered by the attractions themselves. No one skips SECURITY queues, which are common at most of the most-visited sites, but which tend to move pretty quickly and shouldn't be as long during the off season.
We've managed pretty well without guides by doing a lot of reading before (and after) a trip but a guide can be valuable, as acraven mentioned, if "time is short and/or you have a special interest that may not be well-served by a mass-market tour" or deep reading. Personal guides are very expensive but there are small-group tours which are very good and don't involve herding 40 people around. When you decide on some of the things you wish to see, the gang here can make some recommendations if you want to go that route?
Also people are recommending the various 3 day passes for museums.
It comes down to the math: having the time and interest to visit enough of what they cover to make good on them. We've never used the Roma Pass but some folks like that one. For Florence, we used a pass which is, sadly, no longer available and which covered us for longer than the current 72-hour version. Still, the Firenze Pass might be a good buy for you IF you make a plan to use it to advantage in its 72-hour life.
Regarding transit which may be covered with passes, both cities are very walkable so we didn't feel the need to use public transit at all in Florence, and have just purchased a couple of single-ride tickets for venturing longer distances in Rome. Do note that NO pass covers transport from/to airports, and please don't consider buying the Omnia Pass for Rome: that's an oft-mentioned ripoff.
Off-the-beaten in Florence? Put your student in charge of those but if you like art, architecture and history, there's enough in Firenze, both in and out the main tourist areas, to fill your week. Many sweet spots are not really "off the beaten" at all but are not visited by the majority of the visitors on the 24 or 48-hour dead run to the majors (Uffizi, Accademia, Santa Maria del Fiore, Ponte Vecchio...) So, what sorts of things are you interested in seeing?