I think, "If this is ok with you, please let me know." is more common. You might hear "for" sometimes, but in some situations it can sound awkward, if nothing is being done for a certain person.

I think the "to you" and "for you" sound unnatural. I would drop the "to you" and "for you" so it'd just be "If this is ok, please let me know." But if you really want to add the "you" part in "to you" sounds a little more natural.

As Matt from the United States said, the second sentence is correct. Have a nice day ! It would be written like this: If this is okay for you, please let me know.