Nick, a mudcat gathering is limited only by the space available to accomodate everyone. You wouldn't be stepping on anyones toes by organising a weekend, the more the merrier and the gatherings don't always attract the same crowds as festivals. They are a way to get to know people so noone should feel that they will be left out. A lot of us do know eachother now but many met for the first time at a mudcat gathering. As to the format, that depends on the venue. There are usually music and singing sessions, lots of drinking and if there is room we have had ceilidhs - we even had some belly dancing at the first Yorkshire gathering!
Where in N.Yorks are you?
Let us know what you are planning so we can keep a space in the diaries.