In December, postal delay decides everything. Rings leave the studio within three business days, then December mail stretches delivery. Allow three weeks before Christmas so the box is under the tree in time.
If you are ordering late, order anyway: on Christmas night, you give the moment, and the box of rings arrives in January. The couple picks their evening whenever they like. An evening for two is calmer in January than between two family dinners.
The artwork ships about two weeks after the evening, often in February. The couple therefore receives the Christmas gift in two parts: the box of rings in December, the artwork a few weeks after their evening.