Change background in bulk

Hiya.

I'm doing a fundraiser at Christmas and I thought I could offer taking pictures of families/children and changing the background to a Christmas scene. 

I am expecting over 100 children. 

I can take the photo on a green screen or a plain white background. 

I have the design of the new background ready. 

I have access to lightroom and premier pro. 

Is there a way I can bulk change all images to the same background?

Thanks in advance 

Oliver