It is interesting to read the Christmas story outside of December. Some observations come more easier outside "the season."
The "Heavenly host" is literally a heavenly army! Heaven was rejoicing at the birth of Jesus. The shepherds caught some of the overflow of heaven's delight.
"This will be a sign to you. . ." implies they were supposed to go looking. "Everyone marveled . . ." implies that the shepherds were quick to tell people about Jesus. These are two great responses -- Seek and Tell.
Joseph and Mary marveled at Simeon's words because he so clearly identified their baby as the Jewish messiah! His use of the Scriptures is impressive.
When Jesus was in the temple explaining why he missed the car ride home, his parents did not understand what he was saying -- the first of many times.