I think you have to contact the resort to get them added to your deed. RCI is just the exchange company and has no power to change your deed. We did it 8 years ago when our son turned 21 and it was $100 back then at our home resort. Then you would have to ask RCI what the procedure is for adding them to your RCI account. In addition to saving on the $69 guest fee, an owner has privileges and more pull if there are any issues than a guest.
When our five year old granddaughter was here last month I booked one of the $199 sale weeks at a resort in Orlando for us. RCI frequently has sales, anywhere from $299-$199, plus tax, for a week long stay and you don't use any points or weeks. Las Vegas is another location that usually has a nice selection of those sale weeks. I didn't see a very big selection of resorts or much that interested me in the current sale so don't assume that what you see now is the same thing you will see every time there is a sale. It isn't just the junk that ends up in these sale weeks. Yes there are some resorts that I wouldn't go to in the offerings but there are a lot of very nice resorts too. I recommend sitting down at the computer with your children and grandchildren and showing them how they can go and not even have to use any of your points or weeks.
If you have young adult grandchildren they can go places even on a young adult's budget with those sale weeks. For Las Vegas is fairly easy to get round trip flights on airlines like Frontier, Spirit, Allegiant, and others that offer really cheap flights to Las Vegas for anywhere from $80-$140. Add in $199-$299 for a one or two bedroom unit that they can share with friends. When our son was in college he and some friends, went to Vegas, Florida, Myrtle Beach and Virginia. He and his one friend would share the king bed in the master bedroom and the other two shared the second bedroom. He charged them enough to pay for the unit with some left over for spending money for himself. I never had to worry about them getting drunk and being obnoxious to the other guests or trashing the unit. Not that there wasn't any alcohol but as an owner himself he knew he had certain responsibilities. It was a cheap vacation for his friends, they stayed at nice resorts and everyone had a great time.