Choosing a ceremony layout that everyone can see

For forty guests, curved rows bring everyone close. For eighty or more, straight rows with a wide aisle keep sight lines clear and let the photographer move.
Leave the front row ends free for grandparents and anyone using a wheelchair, and put a sign for the order of service at the back, not on every chair.
Outdoors, agree the indoor layout too. If the rain plan is ready, moving a hundred chairs takes twenty minutes.