no sling until around 3 lol (4 was when they went to kinder so we weren't minding them) but DH and i would have one each and when at home josh wasn't in the sling only when we were out. actually i put josh in the sling the other day, he's 11, as a bit of fun and i could carry him! he's 5"3 but only weights 38kgs.

your kids are closer in age i think, maybe ergo or something and sling? i know a woman that wore 2 slings for twins... very ingenious.
beckles