The only thing I've found that might be helpful is a company specialise in holidays for people who might need assistance - in New Zealand itself, but they seem so nice and helpful, if you contacted them they could very likely give you some more information on how to arrange your complete tour. If you click here you can take a look at their website anyway. I hope you have a great holiday.

 If you accompanied travel for seniors this company is the best.
Www.thecompaniontraveler.com
They specialize in door to door service and will plan with you to make the trip just what what you want. They have excellent references and have been in business for three years. They offer a free consult and can be reached at either 505-820-0117 or 802-524-0117. Try them, they are excellent.