Check my 26" vs 700c post in the Newbie's guide above. I think there are three good reasons for you to go to 26" inch wheels on your proposed trip. One is that the tire range you will be most interested in will be the 1.25" and larger tires. That is the range best supported on 26. 26" wheels are stronger, and lughter for that mater. The other is the availability of parts will be far better. However, anything trick in parts will not be available so you probably end up with a draw on that point.

The biggest disadvantage to 26" wheels is that they come mounted on MTBs mostly, and only rarely on touring bikes. There is a touring bike just as surely as there is an MTB or a Sprint bike. And we should probably see them exchanged about as often.

The confusing part of the argument is that the hipster tourers are moving to 26" wheels for some reason, while the hipster MTBers are moving to 700c, sorry 29ers. I'm so confused.

"Wind resistance and weight is gonna slow you down much more so than 1.5" of wheel diameter ever could. Speed of 700c vs 26" has been argued and tested for years and will be from now on and proponents of either size will never concede or agree. "

And that will probably remain until someone wins the Tour de France on sonething other than 700c. However if the Tour was run with self-funded couch guys on 100 pound bikes, with a maximum speed of 10 mph for 99% of each day on the road...