With Benadryl, you may have to play with the dosage to get it high enough to get the drowsy effect. Max takes it for his allergies, 169lvs and takes 5 25mg, 3 times daily, with no change in his activity level or sleepy side effects. Your dog's weight will determine how much you can safely give. Call your vet and see what they think and recommend. We give Jake Melatonin to calm him during storms and when we leave the house. He weighs 98lbs. and takes 2 or 3, 3mg. There are other calming drugs available that are safe to give dogs. You just have to find the right one for your dog. Remember, you are only going to give the dog something to calm them, in order to get them through the adjustment phase and then they take nothing, as they will have adapted to being in the house. The hardest thing to deal with, in my experience, when adapting a dog to something they are unfamiliar with, is to totally ignore the whining, crying, etc. If you pet them or try to physically or verbally calm them, you are reinforcing the very behaviour you are trying to eliminate. By petting or talking to the dog, to get them to shut up, you are telling them that if they whine and cry, you will love on them, therefore, in their mind, they should continue to do this to get your attention. Remember, even negative attention, yelling at them, or scolding them, is still attention and is preferable to an upset dog to being ignored. I'm not saying you are yelling at the dog, just that it doesn't help either. Good luck.
Kathy