I would actually prefer that it not be the second Saturday, if that's not a problem for others.
The reason is that there is a Welsh language walking group - Cerddwyr Cylch Teifi - that is very supportive of learners and walks once a month on the second Saturday in the general Dyffryn Teifi area. If our Meet up is on a different Saturday, e.g. the 3rd Saturday, I could go to the walking group and tell them about our meetup the following week, possibly getting an even bigger number of people along and a variety of people for us to talk to.
So, sorry about it being your birthday, but I would prefer the 17th.
Venue sounds great, by the way, @hewrop
EDIT: Also, the 10th is the weekend organised by Cymdeithas yr Iaith in Tresaith. I don't know if anyone else is planning to go, but they will be joining in with the walking group that weekend.