In advance, you can only book 1 block of time per day. You can book back-to-back blocks of time if more is available once you board. However even if you have back-to-back blocks booked, I believe you must pick them up between and re-check-in again. There have been reports of parents needing to slip out of Palo or Remy between courses to do this.
There is no walk-up entry to the kids club anymore. Well, I guess if they had a spot open during that timeslot you would technically then be signing them up in the moment. But I wouldn't plan on that being available.