Hello, SFB, welcome to Paddling.com.
Celia brings up some good points, especially the pack boat for your wife since she can use a double blade paddle. And a solo boat can be taken out without the need for a paddling partner. You could take your tandem canoe out solo but it’s never as good as paddling a solo canoe. Plus, it’s nice to paddle your own canoe sometimes, married or not.
I’ll add a couple of other suggestions you might consider.
The advantage of a tandem tripper, depending on design, is it will handle bigger waves than your wife might be comfortable handling in a solo pack boat. Canoeing isn’t fun if you’re anxious. The weight distribution in a tandem can be evened out somewhat by having sliding bow and stern seats. You can fine tune the trim with some additional weight behind the bow paddler. This is easily accomplished when the canoe is loaded for a trip. A tandem tripper doesn’t have to feel like paddling a barge if it’s a good design and trimmed properly. But a tandem canoe works best with two paddlers. If you aren’t sure you’ll have someone to paddle with every time you want to go canoeing, a solo canoe is probably the better option.
A solo canoe of similar construction and materials to a tandem is going to be lighter but not necessarily easier to portage. I say that because most solos don’t have a good integrated portaging yoke while most good tandem trippers can be set up with a very comfortable portage yoke. A 50-55 lb tandem canoe on your shoulders isn’t that bad to carry if it has a good yoke. If you don’t plan on long portages this isn’t a big deal with lightweight solo boats. And you could probably find decent removable solo portage yokes for tripping.
One last thought, if you decide on two solo canoes, would be to get a tripping pack boat for your wife and a more traditional solo tripping canoe for yourself. If you enjoy using a single blade paddle the traditional seating configuration is better suited to a canoe paddle.
Have fun in your quest and out on the water.