I thought was getting my almost 13 year old Aussie a companion 6 month old puppy...
I hope there's no statute of limitations for how many times I ask for advice on this sub!
My new little guy REALLY loves playing with other dogs. I've had puppy playdates for him, take him occasionally to the dog park, and I plan to take him to doggie daycare 1-2 x's/wk (it's at our vet and I trust them, and he got high praise for how well he did on his first visit.) Partly because I know he loves it and to tire him out, and partly to try and get him to get out his need for playing with other dogs so it doesn't get turned on my senior.
But, he really tests the boundaries with her. Ideally he wouldn't play with her at all, but I know that's asking too much, but I wish he would play more gently, and listen to her boundaries. She tells him no several times, but he won't stop, so I try and pull him off by pulling up and back on his leash, and if he stops for a second, doing some positive reinforcement, but he usually won't stop. (And, often if he's in a maniacal mood that makes him want to bite me too...) And she doesn't help, because she doesn't make any space away from him once I've removed him from her. If she were younger and less fragile I would let her take the lead. But she's had bilateral TPLO (3 years ago) and her legs are continually collapsing out from her while he tackles her and I'm really worried about her getting knee, hip, or back injury from it.
I've only had him for 2 weeks, and he is officially 6 months old today. I definitely see some progress with him (though he is a bit challenging), and honestly feel like I could make a lot more progress if he were my only dog. My biggest problem at the moment is protecting my senior dog from him. She tolerates him, but doesn't really "like" him. And I think the feeling is kind of mutual. I feel like I may make things worse the way I handle it, but I'm not sure how to handle it better. I usually take him on actual walks by himself because it's too much for me when he starts turning into a little a-hole to have them both. But we wander around my acre yard (forest) a lot throughout the day all together. (That way I'm closer to the house when things go awry).
My senior is a total velcro dog, and wants to be underfoot wherever we are. Partly because that has always been her personality, but also now because she knows we are using training treats like 24/7 and she wants complete fairness in treat giving.