I'm not MassGuy, but I wanted to answer this question as well. I don't see how it can be anything other than premeditated, due to the cause of death (assuming he is telling the truth about the strangling). Premeditation doesn't require CW to have thought about it for a long time before hand nor to have carefully planned out the crime. He had several minutes while in the process of strangling them to decide whether he should stop or continue strangling them until death occurred. When they passed out after a few seconds and he continued to strangle them to death for several minutes after, it became premeditated, IMO. And then, he didn't stop at the first one. He made a willful decision to go onto the next one. You don't accidentally strangle three people in the space of a few hours. Three times he intentionally placed his hands on his family members and three times he had an opportunity (4-6 minutes) to realize what he was doing and stop. But instead of pausing or changing his course of action, he intentionally continued until they were all dead. IMO, that is premeditation.
(I know you probably meant to ask "did he plan the whole thing in advance" and I'm still undecided on how much preplanning I think he did. But I wanted to point out that premeditation doesn't require CW to have thought about the crime for days or weeks. Above post is for the purpose of discussion and not directed at any one poster. MOO)