I believe there is no way to compose in the stock Mail app and have the pictures be attachments. Some people, as a function of THEIR e-mail account, will get the e-mail with the pictures as attachments, but that's not a given. So, no way to make the photos be attachments ... using the stock Mail app to compose.
But.
I found this neat app a while ago called "Multiple Attachments" (($1.99, USD). Here's the link:
Multiple Attachments by Jan Mazurczak
https://appsto.re/us/l0dHW.i
What it does is use Apple's "Open In" function to work. As long as an app uses the Share function, you can put it into the Multiple Attachments app (any file, BTW, not just photos). You can just keep loading up the attachments and the app uses your e-mail account(s) to create an e-mail. Then, when you're done adding attachments, you type up what you want to say, add the "To" addressee(s) and send off the e-mail. The app description describes the process better than I, but it sure is an efficient way to send attachments.
For you - it'll be a bit hard to use because you can't use the "Open In" function from within the Photos app. Try it - you'll see. yes, you can open the Mail app, but that's only for ONE photo. And no, I don't know why Apple has the Photos app with no real Share function (!).
So, you'll have to have your photos in another app in order to use the "Open In function. I use the app "Smart Photo Organizer" ($0.99, USD) because you can set it up to automatically sort your entire Camera Roll into folders it can access. From there, it's a simple process to use the Open In function. Here's the link (though, of course, you can use any other photo organizing app):
Smart Photo Organizer by Backpackr Inc.
https://appsto.re/us/xnKNI.i
So, you open the Smart Photo Organizer app to use the Share/"Open In" function to put your photo(s) in the Multiple Attachment app to create an e-mail with attachments. Follow that?
Seriously, though, it's a lot quicker of a process that writing this makes it seem. And, again, it's the only way I know of to send photos as an attachment because Apple won't let us properly share photos.
So, this is one idea. Maybe others will have another (more simpler) one.
Good luck and have fun on your trip!
Marilyn
Edited to add: And where are my manners?! Welcome to the forum. It's good to "see" you and I hope you enjoy your visits here.