Whether or not you can find 700cc rims in another country or not is not the biggest issue. 26" wheels are just much, much stronger because spoke length is reduced therefore they are way more solid than 700cc. Also I would recommend using at least 36 spokes for the front wheel and even more for the rear as this is where most of your weight and stress will be and a higher spoke makes a much stronger wheel. You can make a 40 plus spoke count by ordering a tandem hub and changing the spacing to fit your frame which isn't too difficult.