Ask the boarding gate agent
Forgot to mention this,
Check in early and go to the boarding gate. Politely ask the agent that you and your companion would like to seat together(aisle seats if possible). Usually during check in other passengers are changing seats(some have children not seated together). The agent will try to accomodate families with children first and sometime aisle seats become available or the seat next to the ones that one of you have. Also some passenger might miss this flight and their reserve seats will be released. Must airlines will release held seat between 30 to 20 mins before departure, this is another way you might be able to get those aisle seats.
And like I said, you might be lucky and get a agent who will treat you like he or she would like to be treated and go out of their way to accommodate you.
It usually seems that the female agents will try their best for you.
Even though I have not traveled on Ha to Las, I have traveled on Aloha Airlines to the mainland and a couple of times I did approach their agent(female) to change seats for me and my family and both times they were able to.
Good Luck