The resorts are large. Is there any chance of you changing your reservation over to the YC, so that you can all be together? If so, you could request that your rooms either be connecting or close to one another. The buses stop first at the YC, then the BC. Sometimes, by the time the buses pick up at the BC, they are almost filled, with standing room, only (during peak times). You could, of course, go over to their room and escort them back and forth. All of the facilities, such as Stormalong Bay and the restaurants are shared. No matter which resort they are at, I recommend that you put in a room request, ahead of time, for their room to be close to the lobby, as the halls can be very long.
There are more families with children at the BC, but that does not mean that the YC is adults, only; the atmosphere is just a bit more sedate in the public areas at the YC. The YC is much closer to the boat dock, where you pick up the boats to travel to Epcot, the Boardwalk, and Hollywood Studios, so that may be better for your parents, if they will be visiting those locations.
My personal thought is that it would work out better for everyone, under these circumstances, to stay at one resort. Both the BC and YC are equally good, in my opinion.
BTW, all of the rooms at the YC have full balconies, unlike the BC, where only about half of the rooms have full balconies. The sit-out balcony would probably be nice for your parents to sit out and relax, if they want to take a break, or to just have a cup of coffee in the morning.