My advice would be to step back and think about your intentions for the trip. First and maybe last time going, or a biannual trip? How important are photographic memories to you and your wife? I wouldn't worry about the specific bag - decide what you want to bring, and get the right bag for that gear. A couple examples from my experience...
Next month, I'm going to California with the family. I grew up there and go back frequently. This will be our younger daughter's first time meeting her extended family, something I want photo memories of for us and for her. Not sure exactly what I'll take, but definitely my 5DII, 24-105L, and 430EX II. Possibly the 35L as well. So, pretty light. Conversely...
Early last year we went to China for 3.5 weeks. Photography wasn't the main purpose - we went to adopt our younger daughter.
In deciding what to take, I knew we'd be busy with procedures and of course with a new baby, not to mention dealing with our then 3 year old daughter. But, a photo 'journal' of the trip was important, and I know it will be many years before we go back. I took the 5DII, 16-35L II, 24-105L, 70-200/2.8L IS II, TS-E 24L II, 35L, 430EX II, and a PowerShot S95. The S95 was great for times when a dSLR just wasn't practical to bring, great for another family member to use, and provided piece of mind as a backup - cameras do fail, usually at the worst time.
I just looked over the EXIF stats of the images from the trip. 50% were taken with the 24-105, 20% with the 70-200 II, and 20% with the S95, with the 16-35, TS-E 24 and 35L making up the remaining 10%. I didn't use the flash much at all, but I was glad I had it as the shots I used it for were as fill light for portraits of our daughters. The % numbers don't tell the whole story - looking at the shots I consider my favorites (85 or so), relative to the totals a disproportionately higher number of favorites were with the 35L - it's great on the 5DII as a nighttime walkaround lens. Another point is that most of the 70-200mm favorites were portrait-type shots. There were favs from every lens.
So, my recommendation would be to take the 5DII, 24-105, consider renting a fast wide or normal prime if you don't have one, and maybe a 70-200/4 IS to keep it light. I'd also consider a good quality but small P&S.
Hope that helps!