I would suggest using Poly/viscose for a childs kilt, as it is machine washable. I have to replace my 5 year old's kilt, and am likely going to order it from MacHummel at http://www.canadiancasualkilts.com/

As for a kid's sporran, the ones at kiltstore at very nice, and I would easily order one of those if I wa sordering other stuff as well. However paying the duty on a kid's sporran alone (as little as it may be) seems a waste to me. I would look at Penny's of Thunderbay as they have cheaper kid's sporrans http://pennys.ca/purses.php ($25 cdn for a child's sporran works for me).