I have poked around in some lava tubes at Craters of the Moon in Idaho and they are pretty spectacular.
We also want to see the lava on the big island of Hawaii. We have been to Oahu and enjoyed the sights there but the flowing lava would be something to see.
For me the lava flows would be the only reason to go there...Everything else is secondary. I'm not a lay on the beach kind of dude so I'd be checking our lava, forests and waterfalls...Hiking I guess mainly...Then drinks around the pool at the hotel...And food.
Lava tubes are pretty cool huh! We climbed down into some and they were huge. Of course, they had a fairly even floor due to flooding bringing in silt and mud etc. But in reality are actually tubular...So vast in size though...Hard to imagine it flowing with magma.
Some of the tubes were collapsed and open to the air so you could see just how tall some of them were. Quite impressive.