Helmet always here, too, whether on the one bike with a kickstand or not. My wife used to push back about wearing helmets on rail trails until we came across the concussed woman whose head hit the rock on the ground.
I'm not religious about it - I've forgotten to put the helmet in the car when driving to a rail trail and just did the ride and of course no problem. But, wearing a helmet on a bike for me is just kind of like fastening the seat belt when driving the car - it is not a risk-based decision, I just do it.