I don't have any real advice, but both DS and dd1 would randomly tell me throughout my pregnancy that they didn't want another sibling. Too late by then!! Lol

But even if they had expressed it before that, well, they are kids who change their mind every second of the day so I wouldn't put the fate of my family planning in their young hands - ITMS?

Fwiw - all the kids love dd3 and now fight over whose turn it is to hold her. So I'm sure if you had another baby, she would love him/her just as much as her current sibling. Just my 2c anyway!!!