Convergence holds a special place in my heart. I've never been deeply involved with it, but have gone and performed there many times, especially in the early years before it exploded and became one of the premier cons in the country (to my mind). I'm pretty sure one of my bands (Tramps and Hawkers, maybe?) played the very first Convergence fundraiser.
Here's their policy. It's excellent overall, while acknowledging that some barrier remain.
WisCon, the feminist speculative fiction convention in Madison, has even stronger language.
Universal Design: Disability Access at WisConOutstanding things.
The Disability Inclusion Services offered by WisCon are informed by universal design and disability rights activism. Universal design benefits people of all ages and abilities, by making schedules, communications, and the physical environment usable by as many people as possible. We strive to create an event that works for members in all our physical and mental variety. We must balance that goal against limited fiscal resources, the paradox that sometimes one member's accommodation is another member's barrier, and an entirely volunteer work force. We always welcome discussion exploring how we can better accommodate our members.
1. Embrace of universal design.
2. Acknowledgement of challenges and the "paradox."
3. Desire to always find ways to improve.
Everyone else hosting any kind of professional and/or fan gathering anywhere could learn from this.
More to come!