In my experience , as long as the aircraft is in airport control and you are not expecting them to take your bags for your flight then you should be fine. I have had a experience were i called up EK's call centre on behalf of a family friend who was rather tall and would benefit from the extra leg room and as he was unable to call them himself as he was sick , i pretended to be him
and EK agent was happy to assign "extra leg room seats" with the disclaimer it can be taken away for a family with a baby....
All worked out in the end and he got the seats , maybe give that a go before making the trip to the airport !