Bike for Wife
 

My Wife is 5'2" She has a 26" wheel bike! Should I consider putting her on a 24" bike or fit her on the 26"? Does the wheel size make a difference when fitting?

No difference to wheel size, though MTBs have slightly different geometry from road bikes. The principles are all the same. My wife has a 27" inseam and rides an MTB converted to road with road bars and shifters, etc. There are 47cm road bikes which should fit her.

Definitely consider a 24" wheeled bike for her. I ride 24" wheel bikes at that height, and my view is that far too many people are put on bikes that are too big for them.
The selection of 24" wheel MTN style bikes has improved enormously and there are some very decent options available from Giant and Specialized plus others as well.

EDIT: Now you well may need to fit an extra long seatpost to these bikes in order to ride them properly which is what I have also done, yet the fundamental "fit" of the smaller wheeled bikes is much better.