Hi June,
I've attached some documents that might be of help sorting out some of the language associated with planned giving.
Regarding draft agreements, I would be very surprised if BC SPCA doesn't already have something. I know that both Toronto Humane Society and Ottawa Humane Society have standard agreements and the topic is not uncommon to humane societies.
Perhaps you should touch base with BC SPCA, they do have staff dedicated to planned giving who could help you. As the lead society in the humane movement inside BC, I know that they will have an interest in hearing about your interest.