If you can not get the password(s) from of your son, then you're only option is to restore the iPad. Do not use a restore from backup unless the backup predates the password change; or you'll just put the password back in place.
I hope you have your iPad back up and running with Twerppoet's great advice.
The IPad Forum is a community of members from all walks of life and from all over the world coming together to share our experiences and to help each other learn about this wonderful piece of technology the Ipad. There is a wealth of information already here in the many threads we have so doing some searches will answer most of the questions you have. If then you cannot find the answer you are seeking then by all means post your question. There are many friendly and informed members here only too willing to help you.
Copy all important files (pictures, documents, etc.) elsewhere; either online on to a computer. Most other things can be downloaded again, with nothing more than annoying settings and lost game progress/stats.
Lost passwords are painful on computers/devices. If they weren't, they wouldn't be protecting much of anything.