Should I use a Template? & How to display child pages in parent?

Hello Everyone

I have searched the internet and this site vigorously for answers and have found none so I am pinning my hopes on you to help.

Scenario:
I have a Galleries page, this page has 4 linking icons, these icons are linked to child pages (Ex: Latest Photos, Projects etc.) they are part of the Galleries(parent) page.

I think, correct me if I am wrong here, that the Galleries page is going to be a Template page because of the CSS. I have a specific space in my CSS where the galleries(Latest Photos, Projects etc.) should display.

What I need help with is how to make the 4 child page’s content(the chosen gallery) display in the parent(Galleries) page? And how do I make the ‘Latest Photos’ the default gallery to load when no other gallery is selected?

I am no good at programming, yet, but I hope to learn. I would really appreciate any help. I have read many posts on this topic but most of them only work with displaying a list of child pages or displaying child posts.

Thank you!