Do not wait for them to change course to go around you. The New Zealand Canoeing Association has a list of Canoing sites and other related links. I have been there 4 times with friends and never tire of the area. Bay Kayaks at Lake Waikaremoana. Once again, run by a great team of people who love kayaking and know the area well.
Costs vary depending on the season so ring first.
Last Christmas, a group of us spent 6 days on the lake. In Auckland, there are a number of clubs and Kayaking operations that are good. Julian Harris has a good description of the whole fiasco. Canoe and Kayak run a number of training courses and organise trips to various places around Auckland. Most of them seem to end up at the pub.