It depends on the campaign. If they dribble out the animals piecemeal as you hit certain goals, then no. But if they are just wanting you to hit certain happiness and suitibility marks with a tight time limit, then it's great!
You mean the scenarios? It would work to a certain extent. But then there are some where you do not get more animals until the ones provided are in suitable exhibits. And others where you get only a few animals and no more.
I build on pause when and where I can. I use the suitability guides to get the exhibit right and then add the animals.