[fostermom]

Thank you for trying to help this boy. He does sound like a sweetie. I always leash new dogs to me...it provides an easy and non-confrontational way to monitor/correct behavior, whether it be jumping up on the sofa, countersurfing, rushing out a door first, housetraining, or even monitoring initial introductions with my crew (four dogs and six cats). Usually it only takes a couple of light corrections for an undesired behavior for the dog to figure out what you want and it eliminates the need for huge confrontations (chasing the dog about the house, trying to pry the pot roast out of his mouth he just snagged off the counter, etc) as he never gets to reinforce bad behavior by engaging in it (ie you are able to correct the MOMENT he even thinks about it). Most of my fosters are adopted withing six to eight weeks and I have always been told what great housemanners they have. Remember to reinforce EVERYTHING that you want him to do.
Actually, "teaching" adult dogs is much easier/quicker than with pups or adolescents.
As to the high energy vs geriatric thing, I would carefully monitor their interactions....the one adolescent I fostered was so high energy he was only allowed to interact with my crew for brief periods as he would quickly overwhelm them. Usually females let the males know what they find acceptable (my female would "alpha roll" the adolescent male) and usually the boys are more than happy to comply. I usually am very careful with any interactions for the first few weeks until I see they are over the initial tension of working out their pecking order and they are all getting along fine.
I never allow unlimited/unrestricted interactions until I am comfortable that there won't be a problem.
It sounds as if they should both do fine together with a little monitoring on your part initially. Enjoy and good luck!