Introducing New Dog to Resident Dog?

I have a 9 year old male Husky mix and recently adopted a 2-3 year old male Husky. We have had the new dog for a week and while things have improved, we have noticed that the new dog when he wants to play will mouth or try to nip at the older dog.

My older dog is not really interested in playing to the level of the new one and often backs or runs away to myself or my husband. We have noticed that when the new dog is wanting to play he will go after the rear legs of the older dog and has caused my older dog to wipe out and has yelped on at least one occasion. How can we stop this behavior?

The new dog also like to mouth and bite our hands, but I have seen tips to help correct this that we will have to try. We have 3 weeks remaining to decide if he will be a good fit for us or return him back to the rescue group. I have never had multiple dogs of the same sex so this is new territory for us, in the past it has always been 1 male, 1 female dog both spayed and neutered. Both males have been neutered so that will not be an issue.

I prefer to keep the new dog, but need to make sure I have done everything I can before admitting the situation is not ideal. I know the age difference is not ideal and will have some impact, but I really want for these dogs to be able to co-exist and not be in fear of the other. Suggestions?