This weekend is the 42nd DunDraCon, the long running convention in the San Francisco area. For the second year in a row, a DM is running Beyond the Door to Monster Mountain, a Holmes Basic mini-scenario available on the Zenopus Archives site. The scenario is being run twice, once at 10 AM and once at 2 PM, and is family/kid-friendly. See the convention listings here.
The DM also started a thread about the game on ODD74, where he wrote:
"I will be running this great module with a few added encounters back to back Sunday Feb 18th at DunDraCon here on the left coast. The module by Zach is loads of fun for kids and adults alike and I run it in the room (along with my [wife's] help) with a horde of kids and young at heart in the children's room at the convention. Last year I had just as many adults as kids but it was a hoot. I hope to see some of you there as we celebrate 40 years of Holmes!
Based on attendance this time, if there are slots open, I will allow players to participate in both sessions. Maybe even leveling up!"
For those interested in the history of Dundracon, their website has a great pdf archive of past Dundracon programs going back to Dundracon III, President's Day weekend, 1978.
Here's the cover from the program for DunDraCon IV, 1979 (the cover has a typo which was hand-corrected):