explaining Sam and Tara

Honestly, I think the best way would be tongue-in cheek. After Sidney and Gale reunite, Gale can say she called Sam and Tara.

Sidney: "They're not coming here, are they?"

Gale: "No, they're hiding in a safe place. They deserve their happy ending."

And leave it at that.

If they over-explain, they risk painting themselves into a corner for future installments, should Sam and Tara return