JKRJG24,
We adopted a year-old boxer from a rescue group in March, then recently brought home a yorkie/pom mix pup. The pup thinks he's as big as the boxer, who let's him crawl all over her and nip at her jowls or anything else he can reach.

These two joined the family of an 8 year old cat, 6 year old Llasa and 5 year old shephard mix, with the Llasa the alpha dog. I've found when we want to bring in a new critter, it's easier if we do it away from home territory. You may want to take your older yorkie to the boxer pups to see how s/he reacts to them. If s/he isn't happy about being around them, I would reconsider the opportunity until after the older dog has fulfilled its life rather than add stress. Fortunately or unfortunately, depending on how you look at it, there will be other pups to adopt. But your long time companion only has you.