Kids are pretty smart when it comes to electronics... but if I were in your position, I'd probably go with keeping everything as similar as possible... and also offering a primer on how to use the equipment.
If I were buying the camera for ME then I'd go with the 77D because it offers a bit more technical control based on the control layout. But as this is meant to be a camera for use by a pool of people who will probably be switching bodies and it wont be their personal camera (so how well will they really get to become fluent in the use of it)... then the consistency might be the better choice.
You mentioned many of them mostly just use full 'auto' mode... so those features are unlikely to be used except by more advanced users.
Here's Canon's images of the two camera backs for comparison:
The top image is the T7i, the bottom image is the 77D.
On the T7i you can see four buttons arranged like a circle with the "set" button in the middle. The buttons double up on purpose... for example the top button says "WB" (white balance), the right button says "AF" (auto-focus mode), but when you're in a menu, they also let you navigate the menu choices (scroll up/down or move left-right).
On the 77D the four buttons are replaced with a disk that has a nubby ring around it. That ring rotates. It's easy to roll that real-dial with your thumb while your index finger rolls the front dial. This is also how you can navigate menu choices. The disk with the WB/AF, etc. choices also rocks in each direction.
The T7i has a button labeled "Av +/-" (aperture adjustments) and that button is missing on the 77D (because the rear-dial handles the aperture). You'll also notice the 77D has a "lock" lever below the rear dial.
If you shoot in either Tv or Av mode (instead of Manual) then the rear dial is used to dial exposure compensation up or down. Notice the "lock" lever below the rear-dial... if you flip that lever then the rear-dial is disabled (it wont adjust exposure compensation) for normal shooting (it still works when you hit the menu button to help you navigate the menus). This is for photographers who fear they might accidentally dial in exposure compensation without knowing and just want to set it and lock it.
Notice the main mode dial is on the right of the viewfinder on the T7i, but moves to the left side on the 77D... that's to make room for the top-LCD display.
Also, the 77D has an "AF-ON" button. This is used for back-button focus. Normally both auto-focus and metering are activated by half-pressing the shutter. But sometimes you're following action, someone/something gets in the way, and the focus snaps to that distraction. There would otherwise be no way to take a shot without the focus changing to the distraction because pressing the shutter activates focus. But you can optionally configure back-button focus on the 77D such that pressing the shutter button does NOT activate focus... focus is activated with the back-button (the AF-ON button). These are features that are standard on all mid-range and above models.
The 77D has a control layout not identical... more more similar to what you'd find on mid-range and above cameras (e.g. 80D, 7D series, 6D series, 5D series, & 1D series bodies). The body isn't physically as large as those camera bodies so everything is a bit closer together.