i dont think they will be too big at all !! Ds is 12.5 kgs at 19mths and they fit him just perfect , over the years or so they have till they tt , their body will change shape , so they can go in and out a few snaps but they should always fit , there is a pic in my gallery with my then 11 kg ds in bbh , I totally think you will be fine with the fitteds , so i would check out there sale while its on its 3 for 2 atm !!!!

my advice is buy a few and see if you like them , try them on and go from there ... im pretty sure they will fit your bub just right !!!