a holiday of a lifetime with a 4 year old!

It's sad to see that some of the replies here leave one to believe that many people on this site still have no idea about wildlife conservation or welfare, but still rely on a transmogrification as a typical way of an animal displaying that it's well off.

I'd skip Chiang Mai and head out to Chiang Dao Nest the owners have made a real effort to be family friendly and they have a range of tours/activities that you could join in.

Booking things in advance/paying to volunteer. I take the view it's just a tour, packaged in a different way. I certainly would not pay in advance, you might find you find alternative things to do, or worse still find that you are regimenting your holiday plans around one activity because you've already paid.

Checkout Travelfish for updated reviews of places and accommodation and don't miss my offerings over on Thailand4Kids.

Note that Chiang Dao Nest can also pick you up at ChianG Mai Airport. (For a fee of course, but this is VERY convenient if you arrive later in the day.)

Cheers,
Chanchao