My wife and I live in NC and were actually planning to go to Aruba. But I checked costs and actually cheaper to get a package to Hawaii at similar hotel. Never been there so...
We will have 6-7 nights. 2 islands at the most. We will fly into Honolulu I assume so makes sense to stay on Oahu for a few days to decrease travel, since we've never been.
But we would like to visit Volcano National Park....how would we do that with minimal fuss? Take a flight to the island of Hawaii and spend the night there at the volcanos? Or would 2 nights be better? Any suggestions where--budget not a real big issue, but reasonable. Thanks!!

You can fly early in the morning to Hilo, so a day trip is a possibility, but spending the night in the volcano area would be better. That way, you can visit Volcanoes national park, the town of volcano, and do a night view of the lava, depending on where it's flowing.

You'll have the second day to go explore around Hilo or even go to Kona if you schedule your return flight out of Kona airport late in the day.

Based on Oahu, assuming you'll stay in Waikiki/Honolulu, there are organized day trip tours that take you over specifically to see the volcano. In your short period of time, I think that might be more time & cost effective than trying to do it on your own (since you mention "minimal fuss").

You really only need one night to enjoy HVNP. Fly into Hilo in the morning, rent an econo car, hike all day, hopefully see a lava flow glowing at night (if the volcano cooperates) and fly back to HNL the next morning. You can definitely see the park in a day.

However, if your budget permits, you might not want to check out of your Oahu hotel room that night. That way, you can get away with a carry-on for the interisland flights, which will cut down on travel time and make life easier. Of course, depends on how much you'd be paying for that empty Oahu hotel room for a night. But if it's around $200/night or less, I'd personally bite the bullet just to save the headache.

One other note -- if you don't need to stay past dark, Hawaiian Airlines has flights as early as 7:00 a.m. and as late as 9:00 p.m., so you can easily make a day trip out of it.