If your dad wants to touch the Arctic Ocean, can I suggest you look at flying to Kotzebue instead of Barrow? Not trying to re-plan your trip, but you could fly to ANC instead of FAI, head up to Kotzebue and stay at the Nullagvik Hotel - Nulla?vik Hotel :: Home - right across the street from the (Arctic Ocean) beach (or seawall, beach a short walk.) Then - again, just maybe - take the money you've saved on the FAI/Dalton/Utqiaġvik business and apply it to a flightseeing trip out of Lake Hood in Anchorage. If Denali isn't socked in, the view from a light plane will change your world; if it is, you can fly out over the Chugach Mountains to Knik Glacier, or out over the ice fields around Prince William Sound, or across Cook Inlet to volcano country. https://www.flyrusts.com/

The park road at Denali won't be open as far as the Eielson Visitor Center (opens June 1) and might not even be open at all this year due to erosion this winter - https://www.alaskapublic.org/2019/12...ghing-roadway/

Honestly, I'd take those Denali days and head south to Seward. Visit Exit Glacier, go on a Kenai Fjords cruise (wildlife, scenery) and maybe stop in the old gold mining village of Hope on the way to/from. Google the places on this map for ideas around Anchorage/Seward - https://goo.gl/maps/4LeqvifhVC7gRcuz8

The one-way drop fee to Whittier is huge. But with as many people as you have, one-way cars might make sense, but for ONE DAY only (i.e. swap cars before heading to Whittier. Note Avis is the only show in town.) Otherwise you might look at the train, which is quite scenic.

If you drive the Dalton, pack plenty of bug dope.