My thoughts on the above:
70-200 2.8 L IS II --- I have been lusting after this lens for many years now and I can finally afford it. I would deffo have use for it after the trip as I shoot a lot of portrait and studio work, along with some weddings and events. Trailing through the forums some seem to think this is too heavy for travel? Although we're going to be driving a lot to specific spots so I don't think we'd be walking more than 2 hours at a time. Is the added weight really that bad? (I'm 33 - average build and weight)...
... sold my 17-40 L about 2 years ago, as I just wasn't using it anymore after upgrading to FF from a 400D. So not sure if it's really worth me exploring that end. Doesn't seem to suit my style anymore, I find 24mm plenty wide on FF.
You already answered your own question, IMHO
Go get the 70-200, Steve! You won't regret it. Besides, you know you really want this lens. Range-wise, note that it works fabulously with a 1.4 teleconverter and that gives you a 98-280 f/4 IS
As for the weight, I handle this thing many hours at a time, recently I shot motorports with it (and a 1.4TC II). And yes I felt it after a long day of shooting but that's okay. (I'm 37 - average build and weight) Note that I shoot motorsports with the 7D. The 70-200 balances well on a gripped body.
To carry it around is not too bad. Put it in a good backpack when you're using another lens.
And yes, 24 mm is generally wide enough for everything. I do own the 17-40 and wouldn't want to miss it on my holidays because it's great to get some awesome WA shots, but... when I have the 24-105 on my camera I manage just fine.
For travel I usually pack a 70-300 Tamron USD, but that's because I need room for other lenses and don't shoot much tele on our holidays. My travel kit: 5D2 gripless, 17-40 f/4, 35mm f/2 or 50 mm f/1.8 (mkI), 24-105 F/4, 70-300 Tammy. And a 77 mm circ. pola. filter