Yes i would get a group of juvies(picking the biggest and smallest like MM said) and then return the extra males or ones that are causing any problems. Once they start breeding it will be fairly easy to sex them. Hint* the females will be the ones constantly holding
Make sure you ask the store if you can return extra fish or find a place tha twill so if you do get a group and weed them out you won't be stuck with lots of fish to find homes for.