New Zealand reporting in..... I don't know how much assistance I could provide, as I live in a very small town, and even though we have a very active and avid swimming community, I doubt it would be economically feasible to host a workshop here. The closest "big city" pool would be in Wellington, about two hours away from where I live. But i wouldn't have a clue how to go about rounding up interest ! If you have any suggestions, I'd certainly listen to them.
As for the time of year, does it matter, since it'll be an indoor pool anyway? But you are right, July/August would be the coldest months here.