I'm no expert, but yeah I think you should probably tackle one thing going at a time. I've only used it for poop when first potty training, and then for getting dressed when she was having some clothes issues. But for nursery I would maybe say:
"Hi Eva it's Mummy. I love you so much and you're doing so well at nursery. I'm proud of you, daddy's proud of you, and most importantly you're proud of yourself for going in and being brave every day. You have so much fun with your friends, and your teachers care about you and keep you safe. Sweet dreams, I love you."