Ronda, I take my dogs to a sitter who has up to 10-12 dogs in her home on any given day. At first, especially when Milli was a puppy, I was really worried about how they'd do, especially with the larger dogs, but they did fine. It can take a few hours and a few visits for them to be comfortable with it and figure out their place among the other dogs, but somehow they just do!
To be honest, I would be careful, keeping in mind Teddi's size-make sure you go along with her the first few times to introduce her to the other dogs to make sure you are both comfortable before you leave her for a whole day. I know she has enough personality to take on a St. Bernard
but I would want to see first hand how they separate the smaller ones from the larger ones (even though there is a 25 lb. weight limit) and how they all get along. There is a big difference between 3 lb and 20 lb-but as long as they realize they're all in a "pack" together and the daycare staff won't tolerate any misbehavior, they will all do great together!