We split stays often and although it doesn't work for everyone, we let Disney transfer our luggage, spend the day at a park and return to the new resort well after check in time. You will not have access to your bags until after check in time so plan accordingly and if that doesn't work for you make alternate arrangements. Bell services will deliver the bags to you once you are in your new room or you can pick the up yourselves.
You could also have a few adults move the bags via ride share, store them with bell services at the new resort and then meet the rest of the party after dropping off the bags with bell service to be stored until rooms are ready.