Its gonna be somewhat crowded. It is spring break for about 30 % of the country. The upside is that the weather is not overbearing hot like it is in the summer. Just pace yourself and do a little research. I would recommend getting a copy of The Unofficial guide to WDW by Bob Sehlinger. Has some touring plans in it that will help you a good bit in planning your days so you get the most out of it without feeling like you've just run a marathon.
Have a great trip.
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