Initially the 10 will be fine. The Cons will start to breed around 1-1.5". But like the others said you will need to upgrade the tank size when they get closer to 3". They will still continue to breed but often either the male or the female begins to get agitated by the cramped quarters and will kill their partner.
Hey yeah i think that you can my dad told me i could. 
By the way bud, don't believe everything your dad says... just because he is a grown up doesn't me he knows everything. It sounds like he's been listening to the LFS, which means there is probably allot he doesn't know.