Several parts of Hawai'i Volcanoes National Park are now open. Please visit this website for the most up to date info of the specific areas that you can visit. https://www.nps.gov/havo/planyourvisit/lava2.htm
Please keep in mind that Hawai'i island is the southernmost island of the Hawaiian Islands as well as the southernmost point in the United States. Please bring plenty of sunscreen. Due to the tropical climate in certain parts of the island, bug spray is also recommended to protect yourself against mosquitos. If you plan to hike any trails on the island, hiking boots are recommended, as well as reusable water bottles, and a drawstring bag to keep needed items.
If you are planning on staying at a hotel, look at Costco packages. We have heard great things from other couples who have gone this route, because you can find a package with flight, car, and hotel included for much less than doing so separately. The hotel we recommended is also offered through this Costco package. Additionally, if you are planning to stay at a vacation rental, this will help save you some money. Cost compare between your flight+vacation rental and a Costco package to see what is best for you.