Alaska Airlines complaint: Bumping off return flight

In March 7 of us booked our flights from Portland to Kauai and back. We paid and got our assigned seats. We received info that our return flights time changed which we are ok with. Then received info or return flight is now stop in Seattle then onto Portland again okay with, yesterday my daughter received a message to call Alaska at which time they told her that her and her daughter, and my husband were bumped off our return flight due to overbooking. Devastating. She was told they could put them on a flight back into San Jose with 9 hour lay over, won’t work, she then found a flight on Hawaian Airlines that was leaving close to the time the rest of us were leaving Kauai and landing in Portland around the time the rest of us arrive. She called Alaska and asked if they could get the three of them on that flight, they said she’d have to cancel their flight on Alaska and book it themselves, having no choice she did only to find out it cost each of them an addition $173.00, Alaska never offered compensation or complimentary flights, as it was them who overbooked the plane, and why would they bump my daughter, granddaughter and husband when they already had assigned seat. It’s so unfair as the 7 of us are flying in for a 75th birthday celebration.