We visited Volcanoes National Park and would say it was one of the top 5 places we have ever visited. When we visited we were able to hike approx 3 miles and were able to get very close to the flowing lava. In fact, there were tourists roasting hot dogs over the lava and having picnics. The glow of the lava as the sun went down was beautiful.
We stayed that night in July at a room at the Volcano House within the park. This building overlooks a steaming caldera. It was very inexpensive - around $60 for two. Don't miss this! We are taking our children this April so they may experience it.