Yes, clothes
If you were not specifically told that you can bring a plus one then unfortunately no you cannot bring an extra person.
Same answer as bringing a date
For the ceremony - you will need to pay the day use fee at Heceta Head Lighthouse. Be prepared for a walk so wear comfortable shoes. For the reception- there is plenty of parking at the Hallmark.
Once you park there will be ~1/4 mile hike uphill to the lightkeepeers house. It is a paved trail and the incline is not steep. We are looking into a shuttle situation for those that need it but only one car is permitted to actually park at the light keepers house entrance.