I just read the instructions on a recently-purchased bag of KMart brand
pre-emergence weed killer/fertilizer and find that "it must be applied
before weeds emerge" and that "it is effective up to three months
depending on conditions"?.  So it appears that your desire to spread
just before FL vacation trip could result in success since that is just
over two months before typical crabgrass germination (1 July?).
Watering it in the night before departure would be advisable.

Dad