hmmm....I sense 'doubt' from you and maybe you should act on that and find another way....
4 Months is pretty young and a lot can happen (so to say
) ~ My concerns are the Big Dog and the Teens and the 'Shifting' around of 'where' she will be. To me, that's too many variables for something to go wrong. I would find an 'actual' small doggie sitter or board her at the Vet.