I’m also having difficulties interpretting the part after the comma of this sentence.
雨が降りそうだから、(その人たちに)傘を持っていってもらってね。[持って行く]
It looks like it might rain, so have them take an umbrella (for me).
I guess my problem is remembering that XにYてもらう means: to have X do Y for me, because this meaning is not intuitive for me. This sentence is even more complex because you’re asking someone to have someone else do something.
Without knowing (or forgetting) this grammar point I tend to intuitivelly wrongly interpret it as:
It looks like it might rain, so go receive/take an umbrella from them (for me).
I understand that this:
雨が降りそうだから、(その人たちに)傘を持っていってもらうね
would mean: It looks like it might rain, so I will have them take an umbrella (for me).