The photographer, the DJ and the coordinator each keeping their own timeline is how the first dance happens while somebody is still eating. Move it once and it moves for everybody — no group text at 7pm.
Everyone attached to the event opens the same timeline and sees the same times.
Only suppliers actually attached to the event can see it. If somebody is missing, add them on the event first — that is the permission, and it is the usual reason a photographer says they cannot find it.
Coordinators. This is the thing you currently do in a spreadsheet, and the reason to add every supplier to the event as you book them.