Thanks to all above for the responses.
If anyone is interested, I did find a way to change / lower the volume of the beeps, universally, using the *6 command described in this
link and this
link, depending upon which keypad you have. These links explain how to adjust the buzzer level of a single keypad (mostly tone level) using [*][6][user code] .... However, one of the setting is Buzzer OFF, which is Level 0 on the RFK5500 keypad. 0 can be reached directly from levels 1 and 20 on that keypad, too.
Setting the level to zero on any single keypad did not impact the other keypads. For now, I've just turned off the chimes at the keypad closest to the kids, which applies all day for entry / exit chimes, too.
Wondering if DSC plugin addresses the "keypads" the plugin creates in Indigo. If there is a way to address each physical keypad separately, I could set the one near the kids to level 1, then send *6< to reach 0 when disarming silently in the morning.... Then *6> to return to level 1 for the rest of the day.... If so, that would be great.