For my grandparents' 40th, they flew back "home" (retired across the country), my immediate family drove there, and the six other kids and their families already lived there. The local daughters planned a very nice dinner at an elegant, historic mansion with a private room. No one else was invited, I think, but that was still almost 25 people.
For their 45th, the kids chipped in and bought them a computer and taught them to use it. They loved it!
For their 50th, the kids paid for an Alaskan cruise.
All that is to say, expectations, mobility and desires change a lot over the years. Weigh all those factors, as well as what you two can afford (time and money), and plan or don't plan accordingly.