Nice sentence! It just needs one small fix.
Corrected sentence: The pigeon softly coos, and the animal friends have a great time singing together.
Why this is better (in easy words):
- Only one letter needs changing: COOS should be lowercase: coos. Writing in all capitals looks like shouting.
- The comma before and is OK because there are two whole ideas joined together: The pigeon coos and the animal friends have fun.
- "Have a great time" or "have lots of fun" are friendly ways to say "have great fun".
- You can also put the adverb after the verb: The pigeon coos softly — that is correct too.
More simple examples:
- The pigeon coos softly, and the animal friends have lots of fun singing together.
- The pigeon coos softly. The animal friends have a great time singing together.