My parents are in their 60's and they just got an iPad 2 (32gb 3G ATT). After a lot of consideration, this is what I recommended for them though I would have told them to go with
Verizon -- the ATT part was a fallout of going to
Best Buy.
While I can tell a huge difference in the screen between my wife's iPad 3 and their 2 -- they can't.
In terms of speed, they'll never tell a difference.
The only reason I told them to get a 32 GB was because I knew they were taking a vacation and were going to have a zillion pictures (and they do) and I was going to help them put the pics on their iPad so they don't have to lug 3 albums around (and they do) to show people.
The only reason I told them to get a 3g capable one was simply because they don't fully understand 3G vs 4G vs wifi.... they just "want it to work". I've tried explaining how it all works to them but it's over their heads. I do technical support as a part of my job so breaking things down and explaining them for the layperson is a skill that I possess -- and they still don't get it (but neither do my in-laws). Based on this, I figured I did not want to recommend a wifi only one and then it be MY fault when they find that it won't work at the park and there's no way to make it work (don't even get me started on tethering... that's so far over their heads, planes are dodging that concept).
So it sounds like your parents are in a similar spot. My parents wanted to be able to:
-- Read
-- Surf the web
-- Check emails
-- View pictures of my daughter
-- Do facetime
the iPad 2 is very sufficient for this and meets their needs just fine.