He sent the gift home with Kagome since he wasn't sure that Rin wouldn't find it in her house. As much as he loved his daughter, hiding gifts from her was impossible. He managed to get away with things at Christmas because Christmas was always celebrated at his mother's house. As he dropped her off, he paused and then continued.
"Rin and I are celebrating her birthday with a family dinner. My father, mother, and stepmother are all coming. I'd like it if you came." She gasped realizing the importance of such an event and then smiled. There were some things that she realized she really cared about. Being with Sesshomaru and spending such a nice intimate evening with him and his family was a great way to end the week.
"I'd love to."