Why do you have to say yes? Once a fornight is ridiculous & imo not worth bothering with, Speaking from experience being the daughter of a lazy arsehole who only saw us once a fortnight, I'll never forgive him it.
I would walk miles daily to see my boys never mind once a fortnight !
I stopped joshua seeing his dad for lots of reasons including the fact his dad never turned up & always upset him let him down etc , So i said no more & never regret it since x