i second the advice given for grinding your dogs' nails down. just clipping them leaves the ends sharp (which could be a problem for the riken it sounds like)
when im not boating, i am a dog groomer:
so my edumacated opinion is that using the dremel tool (or pawdicure, although my dogs hate it and i have heard of injuries caused) to file your dogs' nails down is the best way to go: it gets the nails short and smooth. perhaps taking your dog/s to the local groomer and letting her do it would be easiest
we have never had a problem with dog nails and rafts, but the oldest boats ive worked with are late 80's avons, tough as nails. i have 3 dags now, and for awhile i owned a 110 pound rottie rafter who flailed like a fish at the boat when she swam, it was never a problem (she just looked crazy).