The wedding, the graduation, the holiday table. Everyone's braced for the absence, which mostly means everyone's planning to not-mention it very loudly. There's another way: give them a place in the day, on purpose. Absence handled beats absence avoided, every time.
A chair
An empty seat, deliberately kept - at the ceremony's front row, at the head of the table. Deliberate emptiness reads completely differently from accidental emptiness: it says someone belongs here, rather than someone is missing. A photo or their scarf on it, if that helps it read as chosen.
A candle
Lit at the start of the meal or the ceremony, by name: "This is for Grandpa Joe, who should be here and in every way that matters, is." Then let it burn through the event, needing nothing more. The candle does the remembering so nobody has to hold it alone.
A toast
Thirty seconds, early - before the nerves build. "Before everything else: to Mum. She'd have loved this, she'd have had notes, and we miss her." A laugh and a lump in the throat is exactly the right result. After the toast, the day relaxes: they've been included, so nobody has to tiptoe.
Pick one, or all three, or invent the fourth - their song at the party, their recipe on the table, their name in the program. Grief shrinks when it's given a seat. So do they, in the best way: down from a shadow over the day into a guest at it.