It's a bit difficut to correct your note for my English but I'd like to try. 

14ひきの ひっこし - 14 animals move house (Muving of 14 mice.) 

This is my first attempt to read a japanese book so I'm translating it here to see if I have it right.
It's a children's picture book but I need help with the last sentence!

もりの おく めざして、さあお しゅっぱつ。14ひきの ひっこしだ。
Aiming for the centre of the forest they now depart. 14 animals (mice from the picture) move house.

(*さあしゅっぱつ。is like "let's go!" In this case' I'd translate "14 mice is moving" or "the moving of 14 mice".) 

よいしょ よいしょ、みんな がんばれ。おっと、しりもち つきそうなのは だれ?
Hiho hiho (alley-oop / yo-ho) everyone is doing there best.( Husband, who did you fall on your bum with?)!!!

(*みんながんばれ is for cheering them up directly, like "cheer up / Go for it!".)

In this case, おっと = oops! 

しりもちをつく = to fall on one's behind/hips 

〜しそう = be about to 

Yo-ho, yo-ho, Go for it, everyone/boys! Oops, who is about to fall on one's hipps? 

I hope you understand my English.