When I built my cargo bike, I decided to put on a 700c wheel with 27" forks.
A couple of reasons. Obviously the 700c (29er) wheels are easier to find, especially with alloy rims. The other reason was that I could then put a 30-something tire in without worrying about clearance.
It works great, although I am right at the max of the stock centerpull brakes. If I keep the calipers, I should probably grind about 1/8" from the bottom of the slots to allow the brake pads more clearance from the rubber part of the tires.