Any lava-related activity will be found on the big island of Hawaii. The island's main airport is Kona but if you can fly to Hilo, that's closer to the action. Alas, there's no way to predict exactly where the flows are occurring or even if they are occurring (at the moment, no lava is flowing into the ocean).
Access to the most recent eruption has been from either near Hilo or inside Volcano's National Park (
Hawai'i Volcanoes National Park (U.S. National Park Service)). Access can be tricky: the Hilo side access is easier but I get the sense it's more regulated by the locals. The National Park side access is much much more strenuous and the Park Service tends to discourage people but if you are prepared for a 10-15 km serious hike over stunning undulating hillocks of recently formed planet Earth, you may be able to find the flow and poke real live real hot lava with a tripod foot. It's a day-long hike because there absolutely no trail, no landmarks, and no way to hike in a true straight line. I'd not hike the park side lava fields at night -- too many opportunities to trip and the recently cooled lava there tends to have a surface that's like broken glass.
Even if there's no accessible eruption activity, the area and the park are beautiful. The terrain shifts between low rainforest (treeferns & the like) to scrub desert. There are many shorter hikes that provide access to recent craters, thermal areas, and young flows. Lots to see and photograph!
In Hilo, you can also arrange a helicopter tour over the eruption zone. Some tours have a doors-off option so there's no nasty scratch perspex between between you and the landscape. It's a blast!
Have a great time!