When left to his own devices, the celebrations Ken plans tend to be quiet, stay at home affairs involving cake, wine, and sometimes a movie. But on the other hand, he's been quietly worried about Ivy since their fight following Arthur being over to dinner.
He's given her the golden rain tree (that's hard to keep hidden, really), but not her secondary gift, yet. He doesn't hurry through his work, because that way lies mistakes and the necessity of doing it over again; he does, however, defer until tomorrow anything that can legitimately be deferred.
Even once he's finished, he lets her read for awhile. Ivy seems peaceful, out in the shade of the tulip poplar. Eventually, when he feels it's time, he goes out to join her.