Oh yeah, the grandmother is awesome enough to do this. In fact, I'm now convinced its the grand mother, on the sole fact that the jester who is a former knight, immediately wanted to take Sansa to safety as soon as it went down, Nonna Tyrell likes Sansa alot as we seen. But this is not exactly good news for her family, tactically speaking, even if they are in strong position regardless, but maybe she's against her dumb husbands interests (not even sure he has interests, she has him whipped completely). Or maybe she just thought enough is enough with this deplorable excuse of King.
To think of it, what she said to Sansa at the wedding, about Robs death, and how men shouldnt have an added fear in their own weddings just got more hilarious
Little finger, I'm not so sure about, if he would be this ballsy, but if he is, I would get his motive, its defenitely against his interest that the Tyrells and Lannisters solidfy their bond completely with this marriage, and he wants Sansa for himself, so I could see him being clever enough to do all this (break up big power alliance, frame Tyrion, get the last supposedly alive Stark member in Sansa saved away for himself to claim the north etc).