Increased experience can have some pretty dramatic improvements to air consumption but the lung volume difference will still be there. Taking a sidemount course might be a big benefit that you both really enjoy. Even an extreme difference in air consumption could be easily offset with one vs two aluminum 80s (or preferably tanks sizes and types being relatively proportional to body sizes and desired buoyancy characteristics). Notable side benefits being a good sidemount instructor will help you both have a setup that is more comfortable and streamlined, refine your weighting, small tips on reducing air consumption based upon observing your actual diving, etc, etc..
Sidemount mostly likely isn’t going to help the OP at all when vacation diving. Most ops seem allergic to SM from everything posted.