Oh, this bugs me now. About the only reason I can conjure for Cliff hiding Pam's death from Bobby and Christopher is that he was keeping the information to himself to sort of hedge his bets in case things came to a head and J.R. forced him out of Ewing Oil (Cliff ended up quitting in disgust over the oil tanker fiasco in Season 13). Otherwise it just doesn't really jibe with his character as he was written at the time.
Here's another hole in the scenario: Cliff got all despondent when he got back from seeing Pam at the beginning of Season 12; while he was in this funk, he sold Barnes-Wentworth and all its assets to Westar. At that point, once he found out Pam had died, wouldn't that mean Christopher inherits 1/3 of the huge pot of money Jeremy Wendell paid Cliff, since 1/3 of the company was still Pam's? While I could see him wanting to keep the company from Christopher, he's got no reason to keep the money from him. Yeah, Cliff and J.R. continued to butt heads until the end, but his relationships with Bobby and Christopher were always still friendly; indeed, it was Bobby's heart-to-heart that appealed to Cliff's inner sense of fairness to rule that neither Ewing nor Westar was liable for the tanker accident. Meanwhile, fast-forward to 2012, and Cliff not only still has Barnes-Wentworth (did he buy it back from McKay after he suckered J.R. into selling his half of Ewing Oil at the end of Season 14?), but he's grown it into a huge conglomerate.
This has been the problem with Cliff since the new show began — remember last season, and we were trying to figure out just when
in the late '80s Cliff would have had time to go to Pakistan and rescue a street urchin, take him into his family like he's his own son, and bring him up to be his feared right-hand man, Captain Rob— I mean, Smilin' Frank Ashkani? They're rewriting things into Cliff's history on the original show that just don't fit.
or, I could remember what Joel and the 'Bots tell me: "It's just a show, I should really just relax."