how to unlock iPad after my Dad died

O.K. - I bought an iPad back in late October 2011 (yes, over three years ago) and used it happily until January 2014 when I sent it up to my Dad for him to use - I had bought myself a new iPad MINI. Well, he was sick in and out of the hospital. In late February 2014 I went to see him in the hospital and set him up with an Apple ID and updated the iPad ... and installed and turned on Find My iPad because I was worried about the thing getting stolen.

So, he died in March. Retrieved the iPad, and was talking with my step-mom about giving it to her son to use. I went to set it up for him ... and got locked out. I couldn't find the piece of paper where I had carefully written down Dad's passwords. He told me how he usually constructed them, so I have run through all the likely ones, but no good. I tried doing the security questions - but apparently we didnt put his actual birthday in and without the cheat-sheet I cant remember what we did put in.

Am finally getting a chance to make an appointment at an Apple Store - but it says right on the appointment slip that if Find My iPad isnt turned off, then they cant help me. I dont want to pony up $29 for an initial chat or phone call just to be told they cant help me either.

It would be great if I still had my receipt from when I bought it - but havent been able to find it and am pretty sure it got thrown out.

ANY constructive suggestions?