DD is 5 years old and will need a proper bed soon. She's currently sleeping in a cot-bed bed but her dad is very tall so expect she might be too. Should I go for a single bed? I quite like the idea of a bed that transforms into a double bed (for guests and sleepovers when she's old enough) but the reviews online all are along the lines of they are rubbish. I thought maybe a queen but then that seems very big for a kid? Any suggestions?