You'd probably be better off of the mods moved this to the AA forum. But I do believe that AA allows one way awards so you can book a single on-way with your wife's miles and then the other 3 one-ways with your miles. If you are just searching for your award flight at AA.com, you won't see partner award availability. Remember that you can book travel on any One World partner airline, so if those have availability then you can call to book them. British Airways search tool is great for looking for partner availability (or something like Expert Flyer or KVS Tool which require subscriptions).

The Points Guy also has a great blog with a few good guides below. The British Airways post isn't specific to AA miles, but does cover booking within the One World Alliance.

Maximizing Stopovers, Transfers and Open Jaw Ticketing on American Airlines Awards
How to Use British Airways Miles: Post 3, Understanding the Oneworld Alliance