It's not that Epsom salt and coffee grounds can't help; it's just likely they won't. There are exceptions to this. If your soil is deficient in magnesium or sulfur, Epsom salt won't immediately fix a deficiency, but it will help with it over time. Coffee grounds will add a bit of nutrition and organic matter to the beds.
Neither are the wonder fixes they're often touted to be, though. I compost all coffee grounds...it doesn't hurt to add them directly to a bed, but it's not likely have an immediate or significant effect.
I see Epsom salt promoted as a spritz, added to beds when planting, and as a magic cure-all so often, I was compelled to create this a while back:
Given the choice between coffee grounds and Epsom Salt, I'd say that coffee grounds do more good than Epsom salts. Most people don't even know why they're applying Epsom. (or even what's in it)
You can never go wrong with adding quality organic matter to compost. And coffee grounds are some of the best compost.
PS - sorry about your kids and the 2nd grade. On the bright side, if they haven't made it out by age 21, they'll automatically graduate.
Edited by solid7, 09 February 2017 - 09:38 PM.