If it is just a question of making the actual booking , then I wouldnt have thought the method matters .
On the otherhand , if you are still looking at hotels , villas , location , price etc , then I would try all mediums , whether it is travel agents on the high st , travel agents on the net or directly to the holiday companies , and see who comes up with a package that you are happy with , in terms of price / location etc
Check out flight BA or Virgin, Fly Drive.on the internet
Check out Villas for rent in Kissimmee (very close to Disney and Universal Studio) on the internet
Check out Travel Supermarket for tickets to Disney and Universal, (7 Day pass) on the internet
If you are happy then Book them all and away you go,
Thats what we done this year, the above is assuming that you have a family and are happy driving in the USA. (cost wise)Tickets are more expensive if you buy them at the parks etc when you get over there,It is possible to purchase tickets cheaper from outlets in the USA but best to get them over here before you go,.
Have a GREAT time
Last time I went I was very impressed with the prices at www.travelcitydirect.com
You can get tickets, etc from them - everything you need - but I'd try e-bay first. You have to be careful, of course - don't by any part-used tickets - but I've saved a packet. There are numerous websites and guidebooks telling you where to stay, etc. I'd definitely read up before you book anything.
First time at Walt Disney World (Disneyland is in California) is overwhelming to plan - but fabulous once you get there!
We always found it cheaper to book the flights, car hire and villa separately. We booked the flights through expedia, googled for the cheapest car hire and found the villa through a magazine on villas from a newsagent.
By the way, if you are planning on buying your tickets for theme parks online (which again is the cheapest way we found), the park in Florida is Walt Disney World, Disneyland is in California!