Holidays do not respect your rows. The school break lands on Mom's week, the family dinner lands on your Tuesday, and the afternoon you were counting on for a breather turns into a relay of handoffs. You do not need a new system for it. You need to decide the holiday before the calendar decides for you.
Local option: New Plan Care gives families in the St. Louis area in-home help so a parent can stay home: companionship, help with bathing and dressing, meals, and overnight care. Call (314) 405-0887.
Check the rows before anyone says yes
Open the calendar you already use and look at the break as a whole, not day by day. Mark which row each kid lands on for each day, then mark where Mom's afternoons fall. The usual collision is not the holiday itself but the day after it, when the kids are home all day and the plan you made for Mom assumed a school day. Check the school's posted break dates when they come out, not the dates you remember, because schools shift them and you will plan around the wrong week otherwise.
Ask who covers Mom's afternoons
Before you accept an invitation or offer to host, find out what the afternoon window looks like that day. If Mom has a regular non-medical helper, ask whether that person is working the holiday, whether the hours change, and whether the extra time is arranged in advance. If no one is booked, that is the answer you need before you say yes to anything. Non-medical help at home can cover errands and company, but confirm in writing what the helper will and will not do on a day that breaks the usual pattern. Anything clinical goes back to her care team, and the medicine schedule stays with the family.
Name who hosts and who drives
Holiday meals tend to fail on logistics, not food. Write down who is hosting, what time the meal starts, who picks Mom up, and who drives her home. Check whether the house has room for the table, her walker, and the chair she actually sits in, and whether the bathroom is on a route she can manage. If the meal is at your house, ask whether Mom can get through the door and to a seat without a long walk on a crowded porch. If it is at a sibling's house, ask the same questions before you drive over, not in the driveway.
Trade the day back on purpose
When you give up a day on your row, name the day you get back. A swap that is only said out loud tends to vanish by the next break. Put the trade in the calendar with the same care you give the holiday, and confirm it with whoever else holds that row. If a partner or sibling covers one holiday, ask them to cover the next one that falls near their own plans, so the load moves instead of landing on the same person every year.
Read the plan back before the week
Two days before the break, read the plan to everyone who touches it: the kids, the person covering Mom, the host, and the driver. Ask each one what they think they are doing. Gaps show up fast when someone has to repeat their part. Keep the list in the same place as the rest of your calendar so the holiday does not live in a text thread nobody scrolls back to. If you are still looking for afternoon help, Local Help in St. Louis is a place to start.
Ask for the hand now
If the plan has no owner for the afternoon, do not fill the hole by promising yourself you will manage it. Ask for the help while the calendar is still open. Needing a hand on a holiday does not make you failing anyone. It is the planning that lets everyone enjoy the day, you included.