I have a Prius v five (which is the nicer interior and options) and I LOVE IT. I get about 42-44 mpg and it has tons of truck and backseat space. The interior isn't as nice as my husband's Lexus, but the synthetic leather is really nice IMO, and the general fit and finish is better than most, plus the nav and voice control system is great. Definitely check it out.
We did this about a year ago (took the overnight ferry from England to Rotterdam/Amsterdam) - it was very inexpensive, the ship was very nice, and it was a fun way to spend an evening. I found it to be much less stressful than flying (provided you don't have mountains of luggage to handle on the trains) and a neat way to get from point A to Point B. We just booked the cheapest cabin, since we were barely on board long enough to get any value out of an upgraded room. Highly recommend.
We didn't feel like we missed out on any sightseeing time, since the travel mostly took place during sleeping hours anyways. The ship departs pretty late in the day and arrives bright and early in Holland.