Most POS systems will allow you to customize the messages that appear on your receipts, invoices, statements, etc. Some also allow you to specify certain messages that your employees should repeat when speaking with customers.
You need to modify those settings right away. You want to use every possible means of communicating with your customer to promote Valentines per-orders. When someone purchases from you today their receipt should encourage them to order now for Valentines. Your staff should end every sale by encouraging customers to pre-order for Valentines.
It's cheap, it's easy, and it works. You just need to make the changes as soon as possible.
