"Let's go and watch a movie after we get off work tomorrow!"
我们明天下班以后一起看电影吧 should be correct too. I'm a native speaker and couldn't figure out why I was wrong haha.
I mean, "電影吧" was listed as one word instead of two in this problem. I guess we're supposed to go to the "movie bar," 哈哈哈哈哈！
Also a native speaker here, I got this question twice and agreed with you both times.
我们 and 明天 should be swappable in first and second place at the beginning of a sentence.
Translating from English, not sure how I'm supposed to deduce that “let's go" doesn't translate into something with 去 and apparently turns into 一起.
The "let's go" is actually indicated by the "吧" at the end. "一起" just means together. I think that it's also acceptable to use "去看电影吧"。