For Jon Batiste, the thought of playing at the White House was a dream. But even after he got the invitation from the first lady, he wasn’t sure that he would be able to accept. The primary consideration for the 36-year-old musician was whether his wife, Suleika Jaouad, could be by his side. She is going through chemotherapy to treat leukemia; her health was a major reason Batiste made the decision earlier this year to leave as bandleader on “Late Night with Stephen Colbert,” a post he held for nearly seven years. He wanted her with him for this big moment. In the end, the virtuosic bandleader was able to bring her as well nine other members of his extended family.