solent clown
RIP
We towed a mirror (33' yacht) for many years, including on holidays on the Dutch inland waterways (with lots of locks). In general a small child was tasked with watching it during manoeuvres as we had a ready supply. Without a dedicated fender operator you would probably want a dinghy with a good rope fender, and simply shorten the painter up hard. For coming alongside it is possible to put the dinghy alongside the yacht (obviously on the outer side), which keeps it out of the way and allows you to reverse without incident.
I would say that a mirror may be a little large for two, though the ability to leave the mast up while rowing and towing is nice. On the Norfolk Broads they have some slightly smaller tenders with very basic lugsail rigs. These have the advantage that they can be un-rigged for rowing at the drop of a hat. Also have a centreboard so no worry about flooding through the slot*.
*I vividly remember leaping into the mirror mid North Sea crossing to bail after a particularly bouncy night.
Mirror is favourite idea right now as they are available, plentiful, and I have a lot of mirror spares here. That bailing out sounded like fun! I may consider a bilge pump and a long power cable via a waterproof jack plug if we go for it.