New dog?

We have been feeling like Maggie is super neglected lately. She wants to run and play but I just don't have it in me to rough house with her. Cory does a pretty good job when he comes home, but we still feel like she is a sad dog. We found another heeler on Craigs List; the owners had one dog and then got another one but the first one was really mean to him so they are getting rid of him. We brought him home on a trial period to see how they do for a week. So far he is great with the girls, a little scared of Lillie, but not aggressive. He and Maggie are doing ok...he wants to play and she wants to sit around. who knew. I took them on a 2 hour walk this morning and they are both exhausted and laying around. We'll see how the next few days go...