First of all it has to be the twins they pick, if it's not then the rest of what I say shouldn't happen.
But if they do pick the twins, this is what they should do. Firstly, make it a double so that we
definitely get rid of one of Sophie and Sam

but don't tell them that these three are up until Emma talks to the house on Friday (I have a really bad feeling they're going to ruin it and tell them tomorrow, that's boring)
If they thought that the whole house was up and these three were the ones immune, then on Friday night they reveal it it'd be a much better reaction. But how they could make it even more evil and get a much better reaction out of them is by making it pretty much exactly the same as BB6's lie week twist...
The person with the most votes is evicted immediately, and then they announce that it's a double eviction but the housemate that will be evicted next will be determined by the other housemates themselves

(like Makosi VS Vanessa). Just imagine it...the twins have been evicted and they're all in complete shock and then Emma goes and tells them that they must vote out either Sam or Sophie

they'll be in tears
So yeah