Obviously, custom jewelry takes some time to complete. You won’t be able to order it and pick it up next day. While it varies between jewelers, an average timeline may take two or three weeks for completion, while complex projects might take up to six weeks.
Because of this, definitely give yourself a buffer period of a couple weeks between when you need the jewelry, just in case things move on the slower end.
As long as you plan ahead, there should be no issues.