Dublin House is very close to where all the festivities will take place, and it is walkable to many things in Yachats (including walkable to the ceremony and brunch). The rooms are fairly budget friendly, especially with third party rates through Expedia or Booking.com.
Silver Surf is the most budget-friendly (and dog friendly) option we prefer in Yachats. It has direct beach access and little kitchenettes in the room. It is nothing fancy, but we always enjoy our stay there.
The Adobe Resort has a variety of room-types, a restaurant/bar onsite, and direct access to a rocky beach and trails. This is a higher-end choice, budget-wise.
The Eugene airport is about an hour-and-a-half drive away from Yachats and would be the closest airport to fly into for the wedding. I always recommend renting a car directly from the airport for ease of travel.
PDX is a more "major" airport with possible cheaper flight options and more direct flights. That being said, it is a 3 hour drive from PDX to Yachats, so plan your travel accordingly!