How hard is it to cancel 1 person from a dinner show ADR?

[frannn]

Calling tommorrow for ADRs, and not sure if DD16 is coming with us (probably not). It will be DH, DD6, and me. I'm hoping most tables of 3 can accomodate a 4th, and only want to add DD16 to the ADRs that I have to (those that have specific tables for 3 or limited seating). I'm thinking I'll have to add her to Ohana and Boma, CRT, HDD, and Mickey's BBQ. I just want to be sure I'll be able to take her off the ressie at a later date without opening a can of worms (like having to book a whole new ADR, or having them forget to take her off & charge me by accident, etc).