My understanding is that a 700 x 42 mm tire will fit on the Vado SL, but that's not much different than the stock 38. If you go to 650b wheels then I believe a 650 x 47 mm will fit and likely a 50 mm will fit. Whether or not that would make it acceptable to you and your wife is only a question the two of you can answer. I ride both off-road and road, but I have no issues with riding 23 mm tires on my carbon road bike and I've done light gravel in stretches. I am fine with it, but understand many would not.
My guess is that you might be better candidates for something like the Giant Thrive E+ (wife) and the Giant Fastroad for yourself. These bikes come with 27.5 (or 650b) x 2.4" wide tires. I would think that's plenty wide and lots of volume to take care of road chatter. The Giant is cheaper, though it does weigh a fair bit more. I believe it's around 48 lbs or so.