Re: Need advice on purchasing three ATVs
In answer to the specific questions:
Probably 400. Although 300s are not bad (namely Honda 300EX), you will probably wish you had bought the 400 after a while. The difference in price between the two (again, this is Honda) is only about $900. Your son will definitely want a 400, but you could probably get away with a 300 for your wife. The 300 still has excellent power and it has reverse (great feature for females). I say this because my girlfriend just bought a 300EX and she loves it. She wasn't into the whole not-having-reverse thing and she is not as crazy as I am on the 400EX. (They're smarter than we are - that's why they live longer!!!)
Stay away from Kawasaki quads. They make great bikes and skis, but not quads. I had a Kawasaki quad about 6 years ago and it was the biggest piece of junk I've ever owned. Besides, anyone will tell you, Honda is second to none when it comes to durability. They never die.
2 vs. 4WD is completely up to you. Personally, if I were to buy three quads for my family, 2 would be 2WD and one would be 4WD. 2WD quads can go basically anywhere you want to go. Although 4WD quads can go through more, climb more, and pull more, they are not very fun to blast around on. Having one 4WD quad would be a good idea in case you want to tow something or pull another quad out, etc.
As for automatic vs. manual, that too is up to you. For blasting around and jumping, manual is the way to go. Always has been, always will be. But, for torque and ease of operation, obviously, the automatic has its strong points. The reason I say torque is because my automatic Polaris has a belt-driven transmission which keeps the engine at peek on the torque band at all times.
If you are going to go with all Hondas, which I highly recommend, you should get a Rancher 4x4 for yourself (or a Foreman if you want to spend a little extra $$ for a bigger engine), a 300EX for your wife, and a 400EX for your son. I wish my father bought me a 400EX!!
Go to the Honda website to get the statistics for all their quads - you may find something different you like. Also, go to your local dealer. There's no better place to shop than the shop itself. You'll be amazed at what you can sucker yourself into just by seeing and hearing something.
Good Luck - hope I was of some help