Mayela,
Thanks for your question to planDisney!
Absolutely you can book a Walt Disney World package that has a different number of theme park ticket days than the overall number of days that you will stay at the resort hotel. My family always plans at least one no-theme-park day, where we relax at the resort pool, go miniature golfing, or enjoy some other exciting diversion outside of the parks. On a 6-night stay, we usually only would have tickets for 5 park days.
How do you do that?
When you book your vacation package at the Walt Disney World website, start by finding your resort of choice and visit the "Room Rates" page, like this one for
Disney's Grand Floridian Resort & Spa. After setting your dates and party size, you will see some reservation type options at the top, including "Room Only", "Package" (which would include theme park tickets), and any special promotional offers that might exist at the time. After you pick "Package", you then select the room type. Next you select the number of park days you need. In your case you would have a 7-night hotel stay but will select just 3 park day tickets.
BONUS TIPIf you are on your actual vacation and decide you want to add another park day, you can do so. Just visit the guest services desk at any of the parks and they can help you out.
Write me back if you have any follow-up questions.
Have a Magical Vacation!Doug