Kim, A personal question if you don't mind. How do you cope with conversations with others while on a bike? This seems to be being billed as a very social ride, but with my hearing, holding any sort of conversation while on the go is just not going to happen.
As a hearing person with rubbish auditory processing, I find the biggest problem is wind noise and not being able to hear someone who's in front of you as easily as someone behind - but most hearing cyclists are used to that to some extent - especially helmet users.
When riding with barakta I wear an FM transmitter under my jersey (keeping the microphone out of the wind) that links to her hearing aid. That means that as long as she's within radio range (100m or so) she can hear me reasonably well (though I tend to simplify my language to make up for lack of lip-reading), and as the radio link is only one direction I can't always hear her reply - particularly if she's riding in front of me. She often responds with one-handed gestures (not all of them rude) when we're riding in single file. It can be awkward if we get separated in a group, as she can't hear the people immediately around her without faffing around with input settings.
I've cycled with BSL-using friends a few times. In-motion conversation tended to be limited to simple things like directions, pointing at interesting things (amusing signs, potholes, dead badgers, etc), "everything okay?", "slow down you fit postman bastard!" "your bike's making a noise" or " I'm going to stop up there" which can be communicated one-handed without riding into anything. As a mixed-ability group we'd stop a lot anyway.
Appreciate that it's going to be even harder in the dark.
On the other hand, even on social rides, plenty of people just get on with turning the pedals for prolonged periods.
I don't think there's a magic solution to this one, other than deaf awareness by your companions. Which could be fine if you're riding as part of a YACF group (or whatever), but doesn't work so well with random strangers.