@JohnSnow
I know I gave you some advice earlier, and I'm not sure if it's been covered yet, but I would be remiss if I didn't mention the following.
As I've mentioned before, I've streamlined and modified 5e for an older group to make it more like TSR-era D&D. A lot of the simplifications and houserules are beyond the scope of quick advice, but I definitely should mention that there is another source of advice...
The 5e DMG. That's right, as we all know,
no one reads the DMG!
But there are a bunch of optional rules in there that might help. One big one is the "gritty realism" variant.
It changes long rests to one week, and short rest to a night's rest.
It makes healing more important, and it lowers the amount of casting and "going nova."
A few notes from running it-
1. It doesn't solve the "attack cantrip" problem, to the extent that you believe that this is a problem.
2. In regular play, short rest classes are at a disadvantage; with this, short rest classes shine. If you use the rule as written, certain classes (monks, warlocks) under the 2014 5e rules will pop in a major way. If this becomes an issue, you may need to limit short rests (once every two days).