Hamsters do not live in social groups. They generally dislike other creatures.
Guinea pigs and gerbils thrive in the company of others. It is cruel to keep them alone.
Firstly, this is the best advice ever, especially if you have young children. Guinea pigs are pretty hardy and much less skittish. Hamsters are fast, wriggly and much less child-proof!
If you get a Syrian (golden -the large, regular ones) hamster only get one. They will fight, eat each other or multiply. You don't want any of those things.
If you get Russian/Chinese dwarf hamsters, they are okay in pairs of the same gender if they are from the same litter.
Your breeder should be able to advise you. My advice is to get two guinea pigs, or one Syrian hamster.