While at first glance it seems like the nice Pappa and Mamma are tricking us, let's think a bit.
In no moment they have pretended to be anything else but the leaders of a M.C. with the ruthlessness and strength that comes with it. If the death of the Minion and anything else of their plans wasn't clear enough, neither Stan nor Della, stop at anything to avenge the murder of their son and his wife.
Yes, they are affable, loving and caring, but there's unyielding steel in their resolve to destroy Barb, Willie and all the Minions, not only for Bob and Sissy, but for each and every slight and strike since.
When Jessy and the others find a ring in a place so many of them had already searched, after so many years, a silver ring even, with no signs of ageing, no dirt, still shining... you didn't have alarm bells ringing? It was obviously planted.
Did it do what needed to do? Yes. Angelica needed that push, yes it's underhanded, but it worked.
If anything, this raised my opinion of both Stan and Della. They are going all the way. They no longer have the time to play fair. Stan is getting weaker every day. They either go now, or never and the Rogues are over.
I wasn't tricked, I was delighted actually.
Peace