T.F.
Have fun....You will love it... YES your 4 yr old will have fun!
We always stay on the monorail line, specifically at the Polynesian. We started going wwh daughter (now 14) was 2 and went at 2,4,6,8,10,and 14. Each time she has enjoyed newfound things for her age.
One perk of being on the monorail line is easy access to MK and special buses to other parks. Also, we were able to go on a semi-private safari (conceirge guests) which was the biggest hit of our last trip in March 09.
The Character dining is fun...Contemporary resort has Chef Mickey which is All American buffet, Polynesian has O'Hana with Polynesian theme and 1 luau is Character. We've always enjoyed the more traditional luau which is great. There is a boat shuttle to MK from Grand Floridian and Polynesian.
Fireworks at night from Cinderella castle, 3pm daily parade is a must, 7pm light parade is fun.
I do all of my booking online with WDW resort OR the WDW customer service directly. You can also get an informational dvd from WDW so you can make choices. I deal directly with our airlines for tickets and WDW for lodging/tickets/misc. I know there are some "deal" sites out there, just be wary...if it sounds too good to be true....you know the deal... Our motto when we go on any vacation is to "do it right". We don't purposely overspend but we don't go cheap.
The tickets we buy are hoppers (I think)...they are good from the time you check in until after you check out.
We fly to Orlando and take a private cab (about $80) to our hotel. They do have free shuttle service but no guarantee on how long it will take you to get to you destination because a lot of people take it.
No need for a car, especially if you are on the monorail line. We have never stayed off the monorail line so I can't answer anything about resorts other than Polynesian (our favorite), Grand Floridian (the top resort, country clubbish, very nice) and Contemporary..(cool place because the monorail goes through it.
Enjoy and feel free to PM me if you want more info.