DH, DC (3 months) and I were flying for the first time today to see family, long expected break!
We had booked priority, lounges and everything we could to relieve a bit of the stress.
Priority queue was quite long to check in luggage and we started queuing nicely.
Another mum came along and told us we could jump the queue which we did gladly as baby started stirring a little bit.
However it enraged some of the people in the queue, literally shouting that it was very out of order and that was no such thing as baby class, and what is wrong with you people etc.
Interestingly, every other step in the airport (security, customs, boarding) we were invited nicely by the staff to jump the queue.
So YANBU, of course you can jump the queue when with an infant
YABU no, you should queue like everyone else