Dear Mark,
Thank you for your email. It's great to hear that the BSA wants to support early career sociologists. Honestly I think all of the things you listed would be appealing, though as I'm currently arranging a conference, additional potential sources of funding to apply to would be very beneficial (I have applied to the BSA event fund). Further, I think there could be space for specific guidance on different ways to make the most of a postdoc. Events looking at topics such as the process of turning one's PhD thesis into a monograph, and the various (relatively under-emphasized at the postgrad level) processes of finding funding and writing funding bids.