Will my Betta fish get along in this aquarium?

I currently have my Betta fish in a 10 gallon aquarium all by himself, he's incredibly friendly and even lets me basically pet him haha. But I just got another 10 gallon tank which has 3 tetras, 1 platy, 2 cories, and 1 dalmation something, molly maybe. The previous owner took great care of them and they all get along amazing. But I don't want to have two 10 gallon tanks in my room. Can I put the Betta in with them, or will that be 1) too many fish in a tank (it doesn't seem crowded at all, plenty of hiding places) and 2) dangerous for my betta?