I think kittycollars are recommended for cats over 6 months, I found breakaway collars were too big for kittens even if you can get them to go small enough round the neck as my two kept getting their jaws trapped when they were little. I waited til they were a bit bigger then started putting them on for short periods every day, 10 minutes to start off with then gradually increasing it. I would definitely lose the elasticated collars and wait til they're a bit bigger before trying the breakaway type. I'm sure with a bit of persistance they'll both come to accept them.
My boys are completely at ease with them now, they don't wear them in the house but when it's time to go out I call them over and they come running to have their collars put on. Lucas normally gets his off within minutes but it's completely intentional, it doesn't bother him in the slightest it's just that he knows how to get it off so does!