I'm spending the last week of April visiting my daughter on Maui and we are planning an overnight trip to the Big Island to see the volcano. We want to spend time after dark viewing the lava or glow. Is it worth getting a room for the night or can we just crash in our car for a few hours?

Not sure what you mean by crash in your car for a few hours, nor if they allow that in the park but, it is worth the going and one piece of advice make sure you take a couple of flash lights, it is beautiful and well worth it nice pair of hiking shoes would be a must. What ever you do do not wear open toe shoes, when I got out of their my boots were all scratched up

It is definitely worthwhile. Check the volcano observatory website for current conditions. The lava flows do change and the hike to see it may vary. This is a difficult hike in the dark because the surfaces are very rough and uneven, no trails and no light.The hike, however, is most spectacular at night, not quite so during the day. The drive back to Kona or Hilo is longish, and roads winding and narrow. Would consider staying the night in Volcano village where there are numerous B&Bs. You could also spend the daylight hours hiking around the other sites within the National Park.

Spend the night! Kilauea Lodge would be a good choice.

this site gives nearly daily updates of the lava flows...

http://hvo.wr.usgs.gov/kilauea/update/main.html

We were at the Park in February. Drive to the end of the road to do the hike just before sunset, watch the sun actually set and then enjoy the volcano flow/glow after dark before hiking back. Be sure to bring flashlights and warm clothes. The Volcano House in the National Park is a nice place to stay. Get a room with a view, it was pretty spectacular. It is a quick drive to Volcano Village where there are a couple of great restaurants. The Thai place and the Pizza place were good for dinner and Cafe 100 I think it's called was a great place for breakfast.

Lots of information here:
http://www.nps.gov/havo/visitor/camping.htm

The visitor's center does a good job of educating tourists about the volcano and its significance. There are also several hiking areas in the park that are unique, and well worth seeing. The lava viewing area is 45 minutes drive into completely barren lava fields - hot, dry, and no facilities - so you won't want to "crash" there for the night.

The week we are in Hawaii, there is a full moon,does this help or have any effect on the night hike ?

It wasn't a difficult hike when I did it. I recommend waking up really early and hiking in (in the dark and watching the sun rise!!). one of the most magnificent sights i've ever seen

You should hike out before the sun set, and stay for the night. We brought headlamps and hiking poles. The poles really helped. You could get one from Wal-Mart for only $10 and it's collapsible.

We stayed at the Volcano Inn on 2nd Street that a lot of people were skeptical about, because it had the same name as the other famous Volcano Inn. But it turned out great, and we had a fantastic cabin w/ huge windows looking out to the rainforest and fresh flowers in the room. The room was clean and pleasant, and it was only $65 a night including taxes! It was one of the most unique accomodations we'd ever had on our travels.

I would try and get a room at the Volcano House, which is the only hotel located within the National Park itself. There are a lot of interesting areas of the park-- lava tubes, old calderas,steam vents, a museum--that are accessible if you have a car. It is definitely worthwhile to see the lava flow at night, but, as others have said, the walk can be strenuous. The lava fields that you walk through are very uneven and the rocks (old lava) are very sharp, and I totally trashed a pair of sneakers on the hike. The hike itself can take a few hours, so a long-lasting flashlight, and water, are advised. If you want to extend your stay, there is a beautiful Black Sand Beach in Punalu'u to the south, and there is the Maunaloa Macadamia Nut plantation near Hilo.