I agree with ​​​dark_phoenix that SAS Plus is an absolute minimum + buying/selecting seat assignments. The tray table might be an issue since it doesn't push out that far. As a small person, I've found it to be constricting at times.

Keep in mind that SAS Plus seat cushions (between the armrests) aren't that much wider than SAS Go. Maybe an inch? If you can (barely) fit in a regular Economy seat, then that extra inch might make it bearable. Also, your bulkhead options will be limited unless you are EBG or higher (or *G/STE+, who still have to purchase seats). On the A330, you'll only be able to select 20B, 20E, and 20G in advance, as 20A, 20D, 20F, and 20H will be blocked for status holders.

In SAS Plus, all the aisle seats have adjustable armrests, so your best bet will probably be 20B or 20G, while your wife sits behind you in 21B or 21G or chooses the middle bulkhead in 20E. If the adjacent seats are available 24 hours out, she can switch to one of those.