Great idea Lou... I organised a hap-hazard and not terribly successful thing last year
I had a vision... but we ran out of time to organise anything with short notice
my vision was... to hire the large room at the Grey Lynn Community Centre (nice & central) that opens out onto the kids playground (fenced)... and have a table with sewing and tips on how to sew your own nappies and have tables from WAHMs wanting to be there and WAHMs that aren't able to be there could get someone from TNN to represent them and send smaples/brochures, etc. And have a playpen area with toys for the real littlies and chairs in a corner for coffee and chatting... much like a mini expo specifically for nappies.
I think one of the problems in the past is that we approach it like a public nappiccino... whereas I would like to see TNN hosting something that wasn't for TNN members but for the public to learn. IYKWIM
Let me know if I can help. Just some ideas I had... I have more

Cheers
Janine