Joyride, you’re all sorted now so don’t stress about it any longer.
when you’re not a frequent flyer the small details don’t mean so much to you and you take it all at face value.
I often have my seat assignments shifted, it is unfortunately one of those things that happens. They are never assured even when you pay a fee. You are entitled to a refund of your seat assignment fees.
For reference on your return flight, you may wish to move from row 1 as these seats may be bassinet positions, therefore, anyone travelling with an infant will be assigned the bassinet position seating. Again, ask at the airport tomorrow.