I have been to Mandalay, but before we had a dog and we stayed in a chalet. It was a lovely place and judging by the pictures the camping gound looks great too. I wasnt aware you could take dogs until I saw your thread! I would go back again with ours!
While down there we popped into Four seasons (as we knew we were getting our Pooch and was planning ahead!!) but I wasnt very impressed, I must admit.! It looked very run down and unkempt, but that was about a year ago. I suggest mandalay first then pop into four seasons and have a look, see for yourself.
In Toodyay we stayed in Moondyne caravan park. A great place for someone not as well camped as myself!! It was fairly quiet and the sites were nestled among loads of trees, but it had a toilets, showers and a small kitchen. Everything was very clean. I would definitely recommend it. Its on racecourse road opposite the golf club. Not to be mixed up with Toodyay caravan park as this is the first place you get to as you arrive in Toodyay. Hoever that looked quite good as well. I think they are run by the same people.
This link has both http://www.toodyaycaravanparks.com.au/