Flying with child over 2.

I understand that Delta has a policy against a nonrev flying with a under 6 child in 1st class.
I want to go to the D.R. with my 2 yrs old.
I have taken her with on flights that all had main cabin seats open.

What happens if there are 1st class seats but no main cabin seats left.
Does a main cabin rev passenger get moved or are we denied boarding.
The flights I want to take STI --> JFK there are no upgrades moving up and all nonrev's get 1st class.

Thanks.

Used to be 8 yrs old--the new age is result of NW compromise. They will upgrade very happy revenue pax to sit up front and you will get their seats. Have a wonderful trip and make sure you slather that kid with sunscreen--the sun is really strong down there!

mrs767er is right. We'll find the highest paying customer in the main cabin and offer him/her a first class seat. This will never be a problem.

Thanks for the reply.