The wedding in in the Oakland Hills, so we are suggesting people fly into Oakland airport (OAK).

Southwest has a bunch of flights into Oakland, including from Indianapolis.

You might be able to fly into San Francisco airport cheaper if you find a deal and there may be more non-stop flight options.

Example: I checked for flights IND–>OAK and IND–>SFO on the same days.

The results on Southwest? $300 one way to OAK, $161 one way to SFO. So that is a big difference!

Delta usually has non-stop flights from Detroit to SFO.

If you are adventurous or are renting a car, San Jose can even be an option, but that is not very close, especially with traffic.