Hi! Disney will transfer their luggage for them, but not them. At Pop they don't have bell hops so they will have to bring their luggage up to the front and then have them transfer to OKW. They will have to hop a bus to go to a park for a transfer over to OKW. My suggestion. Hop a cab at POP. We did that last time and it cost us 8 bucks with tip! US and our luggage arrived in 10 minutes! However, we were going from POR to BWV so you can tell them to ask at the front Guest services for an estimate of a cab ride to OKW. They don't look too far apart. When we asked they already had an estimate of what it would cost to take a cab to the other resort. It was well worth the low cost for the hassle free transportation.
Now if they are planning on going to the parks for the day and then joining you all later at OKW then by all means have POP send the bags over to OKW and they can hit the parks.
Hope this helps!