I used this to help the first graders I had during internship learn to correct sentences. We started out with ending punctuation and capitalizing the beginning of the sentence. Then we gradually added different skills such as placing commas in the correct spot and know when to capitalize a proper noun! I would also include words with the short vowel sound we would be learning about during that week. Hope your babies enjoy it as much as mine did!
P.S.: walk around with a play stethoscope and let one of the students working quietly wear it while you complete "Dr. Sentence"!