Besides the RAV4, I believe the Mitsubishi Outlander is the only other truly compact SUV that has a 3rd row, but it's a joke. The RAV4's is also very tight but the Outlander's is a crappy jumpseat-thing. I do like the RAV4 otherwise and that would be my choice if you want to stick with a small SUV. It does not have a lot of negatives, and even the 4-cyl version feels peppy and agile around town. The V6 also gets excellent fuel economy and is quite fast, but is obviously more expensive.
I think you're on the right track with the Mazda5, also. It's cheap, fun to drive, fuel efficient, and very flexible inside for cargo/passengers. It has sliding doors which is a big plus if you have kids. Note, however, that it only seats 6 whereas the RAV4 can actually seat 7 if absolutely necessary.
Unfortunately, both the RAV4 and the 5's 3rd row seats are not where an adult would want to spend much time, which is unavoidable in vehicles this size. You have to step up to a midsize SUV to get a more usable 3rd row and at that point there is no MPG advantage over a Sienna or Odyssey. If you want to keep the mpg over 20 combined with a 3rd row your choices are extremely limited.