Would say velcro. Have you got the hats already? Gap have a lovely boys hat for £8.00 ready velcroed, unfortuately my ds has a large head shape and couldn't fit even the biggest size (age 2-4) - he's only 16 mths!! Eventually got one with velcro from John Lewis age 5-7 years which fits!! LOL Big heads run in my dh's family
Have to agree with the Gap hats - we had to sneak them onto dd2 last summer (she was 13 mths too) if she didn't realise she had them on then we were fine, otherwise off they came. You have to be cunning or wear them down by not giving in - if it comes off then on it goes again.
Now of course she wants a hat on ALL the time, as well as her sunshade and sunglasses - she's SOOOO cool!! she wears them inside too - going for the rockstar look
I need to go to Cambridge to get a kids Gap. The lady there told me if you see something on the website you like, as long as you have the code number, their flag ship store in London can check every branch in the UK and see if they have it in stock and will send it to you for free. I have lost the phone number now but any of the branches should have it.