We have a 100 year old house that we are renovating. The first floor ceilings need repaired. They have lathe and plaster. The plaster is missing from spots and cracked in others. Our plan was to apply 1/2" drywall over the existing ceilings. The worker we hired said he is afraid to add more weight to the 16' long ceiling joists. He is also afraid that the final product would crack easily with the movement in the joists from children rough housing on second floor. Any advice?