If you're adults, I'd seriously recommend the 'Keys to the Kingdom Tour' - although do it on your second day visiting the park - I wouldn't want to deprive you of that 'first walk into MK' feeling.
It goes through some of the finer points of the park and you really get an idea for the amount of attention to detail there is. After that, the park takes on a new role.
The tour needs to be pre-booked and is around $50 per adults from memory, that includes lunch. If I recall correctly, the number to call is WDW-TOUR, or similar and the tour runs on specific days, like wednesdays and one other day each week.
Even if you don't choose the tour, you'll love the park - everyone does.