I would probably get the first season of Mork And Mindy and leave it at that.
As for Happy Days, it's no secret that I'd stop with season seven.
It would be cool if they could have the original promos as bonus features and perhaps a documentary. But for some reason, most of these older TV show DVDs tend not to have much, if anything, in the way of extras.
"Sunday has been cancelled due to lack of interest. That is all."