Sharing a calendar with the people around a child is mostly an exercise in deciding who gets which kind of access, and then being willing to revisit it. The technical part takes minutes. The part that causes trouble later is the decision nobody made on purpose.
Three levels, and most people need the smallest
A shared calendar has three roles. An owner administers it, which means the membership, the settings and ultimately the deletion. An editor can add and change events. A viewer can read the calendar and nothing else.
When you share a calendar with somebody, you choose between editor and viewer. Ownership is the one role sharing cannot hand over; it stays with whoever created the calendar. The instinct is to be generous, because withholding feels rude and the difference is not visible to the person receiving it. Resist that instinct. The school office needs the term dates. It does not need to move your child's dental appointment. Most of the people you share with want to read the calendar and nothing more, and giving them exactly that is not stinginess. It is the setting that matches what they actually asked for.
You cannot share with a stranger, and that is on purpose. Before you can put somebody on a calendar you have to connect with them in the app, which means typing their email address and waiting for them to accept. It is one extra step, once, and it is what stops a calendar being handed to an address that turns out to belong to somebody else.
Saying "you can see, not change"
The phrase to avoid is anything that sounds like a permission slip being withheld. Say what the person gets, not what they are missing: "I'll send you the calendar so you always have the fixtures." Nobody objects to being given a schedule.
It helps to name the reason honestly, because the reason is not distrust. It is that a shared calendar with several editors collects well-meaning mistakes. A grandparent moves the wrong event trying to help. A coach deletes a fixture that has been rescheduled. Viewer access removes that entire category of problem for everyone, including the people who would have made the mistake. Framed that way it is a courtesy rather than a demotion, and it is usually accepted as one.
Access is a decision to revisit, not a setting
Circumstances change. A separation, a falling out, a child changing schools, a coach leaving the club. Access granted for one set of circumstances has a way of outliving them, because nobody revisits a decision that was made once and quietly worked. Put a reminder somewhere to look at the membership list at the start of each school year, or after any change to who is in your child's life.
Removing a member stops the server serving the calendar to them, so nothing new reaches them. It does not re-key anything. A copy they already downloaded stays readable, and no software can unsee a screen somebody has already looked at. Removing somebody is a decision about the future, not an undo.
Re-keying is the operation that does cut off the past. It gives the calendar a brand new key and rewrites every event and note under it, so a copy somebody downloaded yesterday is a copy of a calendar that no longer exists. It is worth knowing how it behaves before you need it rather than during.
It is no longer the blunt instrument it used to be. The new key is handed to every remaining member individually, so re-keying does not lock anybody out and nobody has to be re-added afterwards. The one thing it cannot do is reach a member who has not opened the app since this feature arrived, because there is nothing yet on their account to hand a key to; the app names those people for you rather than reporting a clean success. And everyone still in the calendar picks the new key up the next time they open it, so expect a short gap rather than an immediate change on their screen.
Keep the school calendar and the family one apart
A calendar shared with a school office, a coach and a grandparent has all three of them seeing every event on it. You can remove any one of them later, but you cannot withdraw one person's access to a single event: membership is all or nothing. The choice is between removing somebody from the calendar entirely and splitting the calendar in two.
Separate calendars avoid that entirely. One for the household, one for the school and club commitments you have chosen to publish. Creating a second calendar is quick, and keeping the two apart is far easier than unpicking a merged one. The school's term dates are not private, but your household's arrangements are, and a single calendar forces you to treat them the same.
Onboarding somebody who is not confident with technology
One connection request, one accepted tap, and a phone call rather than an email. That is the entire procedure.
Nothing you send them carries a secret, because there is nothing to send. You type their email address into the app and they get a request to accept; you have to be connected before you can share anything, and the connection is what the calendar key gets wrapped to. That is also why nobody at the service can do this step on your aunt's behalf. There is no link to forward and no password to read out over the phone.
Then ring them, while they have the screen open. Walk through it slowly: accept the request, create an account, choose a passphrase, and you are in. The same conversation is the moment to say the one thing that matters most, which is that there is a recovery code and it needs writing down and keeping somewhere real. It is also the moment to mention that when the request arrives, it will show them your email address — they should know it is you before they tap it, and a familiar address arriving unexpectedly is the thing most likely to make somebody stop. A written instruction waits in an inbox while somebody decides whether to admit they are stuck. A phone call catches that moment instead.