How to reset a deceased family member's iPad without Apple ID access?

Here you go. These are the steps that will need to be done.

How to request access to a deceased family member’s Apple Account - Apple Support

You don't say what you tried to do to reset it. Your options are:

• Go the defined route for this situation and get access to the account so you can unlock the device, as instructed in How to request access to a deceased family member’s Apple Account - Apple Support
• Apple can completely reset a device if a person can provide sufficient evidence of valid ownership. Read the requirements and steps for an Activation Lock support request at: https://al-support.apple.com/#/additional-support and links at the bottom right for the type of service requested. Apple says they may require "proof of purchase documentation” and that you need “proof of ownership documentation”, but does not detail what currently constitutes proof other than it “must include the product serial number, IMEI or MEID.” User reports on this community indicate that typically Apple will ONLY accept an original receipt issued by Apple or an Apple Authorized Reseller. Presumably this is the only kind Apple can authenticate against fraud since Apple is not involved in third party sales. Apple recommends that you "Keep your receipt after you buy an Apple device" --> Keep your receipt after you buy an Apple device - Apple Support