[pdqaltair]

I never felt the need to use both together. Either PFD or harness (yup, I know the law, just ignored it as it does not address harnesses).

There were a few times in very foul weather where I would have my girl wear both; comfort wasn't really important and there were no complaints.

And as you well know, there is no replacment for parental supervision. Heck many guests must be watched.