Go with the medium format. If for no other reason than this gives you an excuse to buy one. I would love a Mamiya 7II. You will have bigger negsor slides and the prints will not suffer greatly from enlargement. COmpare a 35mm neg to a 6x7 and you will see what I mean. Leave the LF at home. You and your wife will have more fun if you are loaded with camera equipment.
In our forays to Vancouver I learned quickly that being able to shoot and move on made the wife happier. And my shoulder did not hurt as much. I use a Hartblei Master 88 and I carry two lenses: 45mm and a 120. I carry three film backs. One for BW-Delta 100 and two for color Provia 100F and I keep a very small supply of velvia and 400NC negative film. This and a light tripod is a fine walking setup.
Have fun on your trip. I am Jealous.