My nephew tried the passcode too many times. Now it just says the iPad is disabled. I have a Windows laptop. Will restoring wipe everything, and do I need iTunes specifically?
Bad news first: once it's disabled, the only way back in is erasing it. Anything not in an iCloud or computer backup is gone.
If it's on a fairly recent iPadOS and connected to wifi, the lock screen may offer an Erase iPad option at the bottom, which lets you wipe it with the Apple ID password, no computer needed.
Otherwise you need recovery mode. Connect it to a computer (Finder on a Mac, iTunes or the Apple Devices app on Windows). On an iPad without a home button: press and release volume up, press and release volume down, then hold the top button until the recovery screen appears. With a home button: hold home and top together until it shows. Choose Restore, not Update.
After the restore it'll ask for the Apple ID that was on it, so make sure you know that password before you start.