When to take baby Pekin ducks outside

[Gtolson]

We have 6 2 week old Pekin ducks currently living in our spare bathtub. They have food, water and a heat lamp. When will it be ok to take them outside to live in their new shelter which we are currently building? We already have 2 adult female and 1 adult male Pekin ducks outside. We have a large pond also. We live in northwest Ohio where temps now are 80s in the day and 70s at night. Thanks!