BB--
Sounds like your plans are what we did last December. We stayed at Hilton for 4 nights (though got in very late so felt like less time) and then drove over in the AM to VNP stopping along the way to see Akaka Falls and get malasadas at Tex's. We waited until we got to HI to finalize our ressies since we were only wanting to stay one night in Volcano. Just to let you know the town of Volcano isn't very large and I'm sure the cottages / inns are only about a few blocks away from each other and a very short (maybe 10 mins or so) from the entrance to VNP. I'm sure you'll be able to find a place within your budget that will suit your needs, especially if you're not traveling during a peak holiday (where they usually require a 2 to 3 night min.. like we had to contend with just prior to Xmas). Good luck.
Carolyn