Possible that travelling with mum soon - I may have business and she premium economy. Would it be difficult for us to swap seats since she would probably benefit more from having bed? Do it discretely and hope no one notices or should I be up front and ask to swap?
I believe that officially you aren't allowed to swap from your assigned seat (because of identifying people in case of a crash, possibly?). But in practice nobody ever compares your id and boarding pass as you get on the plane so you could swap boarding passes after you go through the gate.
Equally, I can't imagine they would have a problem with swapping you over at check in so I would ask then. They might even upgrade your mum !
Speak with the cabin crew as soon as possible after boarding. Preferably not when a gazillion people are boarding behind you, so you hold up the queue.
Explain the situation, as politely as possible, and ask if they would be happy for you to let your Mum have the BC seat. Usually, if they can accommodate the request, then they will. and the nicer, more polite, less entitled you are, the more likely they will be to try to go beyond the strict level of duty to assist They mostly all have mums too
I've done it several times. We travelled on air miles for DH & I but paid for DC & upgraded them. On the plane we gave them our seat numbers Cabin crew were fine about. Oh & they're teens, not littlies.