Most of the time the camera is simply a storage device that stores what the lens sees. Your lenses are letting you down for nighttime football. Especially if it is PeeWee or high school fields where lighting may be less than spectacular. The most important thing to remember in sports photography is location. Not camera. Not lenses, it is where you shoot from that is paramount. Shooting from the bleachers and you are not likely to get Sports Illustrated quality photos. Not even if you have the top of the line Canon gear! Sidelines are best.
Now for the bad news the Tamron 70-300mm f/4-5.6 is a poor lens. It will never be up to the great IQ photos most people want. The EF-S 55-250mm f/4-5.6 IS STM is a good lens actually one of my favorite crop camera lenses but, it also, is not up to night time sports action as a first choice. But you use what you have, right?
As to how to set up the 7D Mk II, it works exactly the same way your Rebel did. However you set it, you can do the same for the 7D2. My preferred settings, to start, would be using Av mode and set the lens to its widest open aperture. Set ISO to 1600 and use AWB. Actually the WB doesn't matter since you will be using Raw file format. Never, never jpg. You have LR so the file conversion will be seamless and automatic when you import into LR. There you can change most settings to your liking.
The one thing you can't fix in Raw is focus. That must be spot on. Use just the center focus point and turn all the others off.
Give this a try and, please, let me know how it went.
If you need a few pointers on LR feel free to ask. I have a few years under my belt with it and PS. 
Clarification on my previous post.
"... use Av mode. You select the fastest aperture possible in your case probably f5.6. This will allow the camera to automatically select the fastest SS possible for correct exposure. Always choose Raw file.
Select a pretty high ISO number (1600). Of course this is for night time games. Daylight will be different."
My second point is know your sport. You need to understand how football is played. If you don't the most important part of this, location, is minimized because you will likely be out of position.
As to lenses the addition of a f2.8 lens will help but will not alone guarantee you get outstanding photos. A lens to consider and a very good buy on the used market is the ef 70-200mm f2.8L. There are three versions and the first version can be had reasonably priced used. You can sell the two you have to help offset this purchase.
Here we have then,
Use the settings above.
Know your sport so location, where you shoot from, can benefit.
Better lens.
Learn Lightroom.
Simple! 
BTW, MsDanaEMc no photogrpher gets every shot.
Enter for a chance to win!
April 20th-28th
