I want to buy a nice outfit for a boys first birthday. I am not sure if I should go with 12-18 months or 18-24. He is quite a big and pudgy baby. Bigger than average but not huge. I want to get something summery that he could wear now. Obviously don't want it to be too small but also not so massive that it won't fit until winter if I go with the bigger size. Don't want the parents to have to go to the bother of changing it. Which size would you go for? Thanks