Travelling after MN1 registration Success

[newuser79]

Hello Seniors,

Have applied for MN1 registration for my under 18 son. We have a flight booked 3rd week of Dec 2021 to travel outside UK for 2 weeks.

If we get the MN1 approval by post before our travel date ( say 1st Dec 2021) - can my son still travel outside UK with his non-UK passport? Is there a specific period allowed for him to travel after he gets his MN1 registration successful before he applies for his British passport

Thanks!