If there's sand all over the place, why not just take a few ziplock freezer bags with you, fill 'em with sand and use them to weigh down the legs?
I've done this and it works well. Easy to carry the bags and they always come in handy for something anyway.
Once the stand is secure and just before the vibes start pushing air, roll
tape digits and 'TAPE IT ON DOWN, MAN!'
Next run of TS shirts, I vote for TAPE IT DOWN on the back.
Afterall, we should never let 'em forget: All your tapes are belong to us!