The answer: Build a sand trap.
That's right. What better way to distract one's toddlers from the pots filled with potting soil but
"The twins need something to do on the deck while I'm outside working." sez Me. "I bet they'd like a sand table! You there! Lazy Husband! Build me a sand table!"
And Lo! He built a sand table using the disused cat litter box I suggested (after I cleaned that sucker back to Factory Clean levels of clean), some scrap lumber and a few wood screws. I then set off for the store and paid $3 for 50 lbs of play sand, since "all purpose sand" appears to not have as many purposes as you may have thought (May contain silica dust. Do not inhale. Not for use in sandboxes.), put it all together and took it out for a test drive.
As for the twins reaction to the sand
They loved it.
Just think of all the great things they can learn from a sand table!
Sand toys = anything you have. Tiny pots with holes. Cups. Spoons. Forks.
My personal favorite thing learned: Sand keeps babies from munching dirt. Instead, they munch sand. Win-win for all involved!
Second favorite: That husband guy is a handy little thing to have around!
Later, in the summer, I will pull out the sand box and put in an identically sized box that has water in it. That way the twins can splash around to their heart's content and (even more importantly) stay out of my pots!
Reduce, reuse and recycle, baby! This may have been the best $3 I've ever spent.