As a WDW cast member, (Disney-speak for "employee") I thought I'd throw my
as well.
Honestly, I'd advise against it. But ...
If you do this, remember
who the trip is for. I have seen countless sets of parents who fall into the "We're paying a ton of money for this trip and you will have fun whether you like it or not!" mentality. With this mentality, you wind up with crying children and parents who are a hair away from a stroke.
With a toddler, you will most likely NOT be able to be at the turnstiles at the crack of dawn (say 8am) for early entry, and stay till the bitter end to see the fireworks and parade at 10pm or midnight without the little guy experiencing a meltdown, or multiple meltdowns.
You can do this trip and have a ton of fun, get lots of great pictures, and maybe even make some great memories for your family. But it will NOT be a bargain. Even with discounted child tickets, you will pay a lot and, if you want to maintain your sanity, you will probably wind up only doing 6-8 hours in the park each day, tops.
Also, bear in mind, you're talking June. It will be hot. It most likely will rain most of the days, so it will be humid. And it will be crowded. Lines at popular "kiddie" rides in Fantasyland will easily be in the 60-90 minute range. You're gonna wind up pushing a stroller all day. Nothing will deflate you faster than realizing "I spent all this money on this trip and this kid is sleeping in his stroller for the better part of the day."
One last tip: if you're gonna have to skip a park, skip Epcot. Not a whole lot there for the little ones.
You MUST hit Magic Kingdom and will likely spend most of the day in Fantasyland. If you want the pic with Mickey, hit Mickey's Toontown Fair.
Hollywood Studios (formerly MGM) is a good bet, especially the Playhouse Disney show. The thrill rides are not kid-friendly. The night show, Fantasmic, may be a bit too intense for a 3 year old.
This post is too long already, if I can be of further assistance, PM me.