Why there is no single number
Two things decide when a card arrives: when it ships, and how long the carrier takes to reach your address. The second varies by destination and service, so a single promise for everyone would be wrong for most people.
Instead, checkout asks the carrier for your address and shows, for each service, the date the order is scheduled to ship and the earliest and latest dates it is estimated to arrive. That is the number to plan around.
How to read the checkout quote
After you enter an address, the shipping options list each service with its price and its estimated arrival window. Standard is the slower and usually cheaper option; the expedited services show earlier windows at a live-quoted price.
If you are ordering for a date, choose the service whose latest arrival date comes before it, with some room to spare.
Planning for a deadline
The safest approach is to design early and check the quote before you commit. Designing is free and there is no time limit on a saved design, so you can build the card now, add it to a box, and see the arrival window for your address whenever you are ready to order.
For a team, the slow part is usually collecting photos from every family, not printing or shipping. Start that early and the order itself can go in as one batch.
After you order
You receive an order confirmation immediately and a tracking email once the order ships. Order status is also visible in your account, and the tracking page lets you follow the parcel.