Hawaiian CC for one trip

I’m planning a vacation to Kauai and Oahu for this August for our family of five from the East Coast. I applied for Hawaii credit card to get the 70,000 miles and 50% off a companion ticket. I’m thinking my husband should open a card as well so we each get 70,000 miles and a discounted ticket.

I’ve never flown on Hawaiian airlines before and I’m not sure if these miles will make a difference in our flight. I’m weighing my options and seeing if this credit card makes a difference. I reached out to Hawaiian airlines to get some clarifications on their terms and conditions, but the agent wasn’t sure if I could use miles and the discounted ticket for the same trip.