I guess because it won't trigger grand celebrations? He can go out quietly and let the appropriate amount of attention fall on his son. No cost to the state for a big fuss before getting a new guy whose own installation will also require some ceremony and public funds. That's my read.
Yes, but could they be leaving before the celebration because she's (they're?) unpopular enough with the people that the jubilee wouldn't trigger grand celebrations with the people? After all, he misjudged his popularity when he refused assent to a law and got himself removed from the law-making process because he doesn't have that kind of respect, and she's known for abusing staff.