Mexico is traditionally one of the more difficult locales for
accessibility. However, Oaxaca, in southeastern Mexico, is a bit
better than most.

This is a good general travel guide:
http://oaxaca-travel.com/guide/index.php?lang=us

For a lot of locales in Mexico, your best bet is going to be a bed and
breakfast on a renovated / retrofitted property with wheelchair
access. This kind of arrangement can offer you the best personalized
service and expert local advice on what local attractions are
accessible.

If you choose Oaxaca, I would recommend starting with the Oaxaca Bed
and Breakfast Association and getting into contact with some of the
proprietors there, to discuss your specific needs and find out if one
might be right for you. The Association website is right here:
http://oaxacabedandbreakfast.org. Though standards for accessibility
are different in Mexico, some of the B&B owners are American expats
who will have a more rounded view of your needs. I’m sure anyone from
OBBA would be eager to help.

You can, of course, get flights directly from Kelowna to Oaxaca, which
has its own international airport.

If you’re in the market for guided tours, then check out what’s on
offer from Accessible Journeys. They offer accessible tours with a
private car and driver and other amenities, centered in Mexico City
and the surrounding areas. I’m sure they can also offer you further
info on contact. Their page for Mexico City is here:
http://www.disabilitytravel.com/independent/accessible-mexico.htm

Here’s a database listing of hotels around Mexico City that offer
wheelchair accessible accommodations:
http://www.travelmuse.com/hotels-with-wheelchair_accessible-mexico-mexico-09-mx

Hope this helps.
Si