I personally think 3 'normal' sized car seats wouldn't fit in a Camry. It's a squeeze in the likes of a Commordore or Falcon and they're pretty spacious.

We have a CX7 and three seats wouldn't fit in it. Nor would they in my parents Pajero. Two would be fine but not three decent sized car seats.

If you're OK with buying new seats, SnS do a great 'skinnier' seat called the Compaq