Fluoride varnishing.. yay or nay?

[ModelVillage]

Our children's centre is offering fluoride varnishing for under 5s. Now someone told me that too much fluoride is potentially toxic..

I would be very interested in any opinions on this. Would you / do you let your child's teeth be "sealed"?

I have discolouration from too much fluoride but I would definitely opt for my DC to have this if it was offered. I was give fluoride drops every day, which gives way more fluoride than a gradual erosion of a varnish.