The reply below is quite formal. I could be wrong, but I don't think we use "have a good day" or "have a good weekend" in Tagalog. I think it would be better if you give them a well-wisher that is more specific. For example, if you know that they will go on a trip to Baguio during the weekend, you can say something like "Sana mag-enjoy kayo sa biyahe niyo sa Baguio" or "Ingat kayo sa biyahe sa Baguio."

nawa'y magkaroon ka ng magandang araw or maging maganda sana ang araw mo.