We just got bunkbeds plus a trundle from IKEA, DS not born yet so is a while before he will be in bunk but bunkbeds plus the trundle gave us most options in terms of beds for visitors and longevity. Most likely DS will go onto trundle for a bit before DD is old enough to onto top bunk but we shall see, I think the notice on the bed says 7 and over for top bunk but I went into top bunk at about four and only fell out once when I was 18 (no wasn't drunk, just sleeping round wrong way to watch soccer)