I have carried dogs, and other livestock, on BA flights many times.
It is not uncommon for the ground staff to inform Senior cabin crew of this fact if the owners are travelling. I always made a point of contacting the customer and reassuring them all was well. This is more important when the flight involves a transit.
I know you have said you are not travelling on the same flight, but please be assured BA will take good care of your beloved dogs and all will be fine.
They may even be on the new 777-300 so very comfortable!