The correct answers are Let's have a break and watch a movie this afternoon. and I hope we have a great time at the concert tonight!

We often use "have" with certain nouns to describe actions or experiences (like have a break, have a party, have a good time, have a shower).

However, we do not use "have" for sports or chores. You play tennis (not have a tennis) and you do your homework (not have your homework).