I just read the lyrics, in this case, 挤一挤means "squeezing more people into the vehicle", because nobody would like to be left. (everybody need to get closer to get more people in, although everybody feel uncomfortable)

Yep, huddle up together. Well put!

应该理解为 "让我们更加亲近".

To bunch up together. The children huddled up together to keep warm 大家挤一挤，取取暖