Have you asked the educators?
I've been an unpaid educator in a "museum" setting, then a slightly paid educator, and finally a very poorly paid educator, although I had a science PhD. I taught children, docents, teachers [including HS level], parents, families. Most of the docents were experienced retired teachers.
One supervisor was a recent graduate with a BA or BS in education. She felt she could provide one single lesson plan that could be used for children from preK to 10th grades - any deviations from her plan led to tongue-lashings for the docents. She knew nothing about what we actually taught, like most people with a BA or BS in education, and very little about teaching people. Docents left the program and teachers stopped bringing their classes. Eventually the institution realized there was a problem and hired a better supervisor. But the complaints of docents, teachers, and their classes had gone unheeded for more than 2 years because...structural problems - don't actually ask the people involved.
Docents want recognition, yes, but annual "recognition luncheons" were a joke - administrators who regularly ignored them and spoke over them said how valuable and wonderful they were but still did not hear them. The money for those luncheons could have been given to the docents to use as they saw fit. Flexible scheduling was very important [we all had lives, oddly enough], but left to ourselves we filled in for each other as necessary; the administrators were the inflexible ones.
"Travel reimbursement, access to training, or inclusion in decision-making" would be excellent. How about extending yourselves, offering training trips to similar organizations in the neighborhood, and offering those institutions reciprocal training trips? Or even places with a different mission, to see how similar/different the role of docent educators is and how they are trained and valued elsewhere...? Join one of the organizations that will give your docents/ educators free entry to other museums/gardens/etc? And publicize it? And certainly offer annual full membership in your organization, so people can introduce their friends and family to the place [and perhaps get new members?].
Finally, after 5 years of being a docent, people should, upon retiring as educators, receive a lifetime full membership in your organization. [Oh, hooror, what a suggestion.] I'm told museum administrators applying for grants use a value of about $28/hour for docent work time. In fact, I learned that on this site. Perhaps you should think about really giving back to your volunteers, educators rather than the lip service commonly offered.
I remember a supervisor of docents and security personnel complaining on this site that people refused to stand in one place for an 8 hour day [very short bathroom and lunch breaks were permitted] because the supervisor wanted them to look available at the entrance of each section. They seemed to want to wander through the section, and sometimes even [what a scandal] to sit down. And to talk to visitors inside the section...
I suggested this supervisor spend the next 3 work days standing in one place waiting for questions/attention/whatever and then discuss with the employees how to do things better. I doubt that happened.
So I will end as I began - try talking to your docents, educators and looking for ways to improve their unpaid service in terms that matter to them.
Meryl Rubin, Ph.D.