There's a difference between the Plumeria Lounge and the Premier Club. The Plumeria lounge is for international business class guests and the amenities are representative as such. The Premier Club, is the domestic lounge which has more basic amenities. It seems though, that anyone can buy a $40 day pass. As for guests, if your guest is over 2 years of age, looks like they have to pay too. See the terms and conditions...
https://www.hawaiianairlines.com/leg...and-conditions
My bad...I meant the Premier Club. But I guess the same guest rules apply to both.