Wow...sad to hear that John's dad passed. Commander Keen, Doom, Doom II, Wolfenstein 3D (and Spear of Destiny), Heretic...LOVED playing those!! Especially the Commander Keen Series...I have every episode from 1, the Invasion of the Vorticons series, to 6, Aliens Ate My Babysitter (and the shareware version of "Keen Dreams")! The 90's 386-and-up games are my favorite.
I bought the complete registered version of 1-5 in 1999 as a CD, and I think it's still available. Unfortunately, Episode 6 (aka Aliens Ate My Babysitter) was produced in conjunction with FormGen software, and FormGen has long been out of business (calling their 1-800 number now gives you a private residence if you can believe that!). That episode did come in the ID Anthology series from ID Software, but it was the CGA-only version. The remaining copies are SUPER-RARE, and I eventually wore the original Episode 6 disks out...can't seem to remember how I hung onto the copy, but I still have it on my computer...that was the first CK episode I played, at age 6!
I forgot the episode number for Keen Dreams (3.5 or 4.5 I believe), and don't know if there's even a registered version...if there is then I would definitely pay some big $$$ for it! The shareware version is pretty primitive, with no music...it's still fun though!
eBay is the place to look for the Commander Keen games...