I'm simply trying to get a pretty good guess on how many grains of
sand there are on the planet for illustrative purposes in a talk I'm
giving. I'd like to be able to site a source of some repute. It can
include any and all kinds of sand. Beaches, deserts, etc. It would be
helpful to know a simple way to relate that to the average person.

Bobbie7,

Did you read your own answer?

First you said there were

7,500,000,000,000,000,000, or seven quintillion five quadrillion
grains of sand.

That should read seven quintillion five HUNDRED quadrillion.

Then in 2) you said there were 

An estimated 1020 to 1024 grains of sand.

Just a little over one thousand grains.

Ansel, you are being picky. Is there really a significant difference
between seven quintillion and one thousand?  There's always a margin
of error. :-)

Ansel001,

Thank you for your comment.

1020 and 1024 should read "10 to the 20th"  and "10 to the 24th power."

Check out the solution here:
http://www.astro.utu.fi/~cflynn/sand.html


And here:
http://www.tufts.edu/as/physics/courses/physics5/estim_97.html

And you are correct, 7,500,000,000,000,000,000 should read seven
quintillion five *hundred* quadrillion.

The question asks how many grains of sand total, not just in beaches. 
There is way more sand in the Sahara Desert alone than in all the
beaches in the world.  See question 587762.

i dont think 7,500,000,000,000,000,000 will be the right answer.
Because there are http://www.worldmostbeautifulbeaches.com/ these much
beaches in the world.
So how we can say ??? Any Justification for that