Separating the bikes

So my girls have been riding their bikes to school in the mornings.  They're 9 and 11 are my two and it's a part of growing up.

In the afternoons I'd been riding to the school and we all ride back home together, but we'd made the call that from yesterday afternoon they could ride home on their own.  It's bike path all the way so there was no concern from anyone.

So I'm at home yesterday waiting....waiting...waiting.  It went past 3:30 and I wondered where they could possibly be, so I jumped on the bike and rode up to the school to find them.  I get up there and they're sitting on the front lawn waiting.  I said "Girls ?! What are you doing ?"

They explained to me that there was something wrong with the bike chain they'd used to lock up their bikes.  The locking mechanism had failed and they couldn't get it undone.  I battled with it for a while trying to get the bloody thing undone, but I couldn't budge it.  I was able to manouvre it so I could get the bikes separated from the little bike bar, but they are still chained to each other.  And so the girls wheeled these two bikes home while they were attached by this chain.  It was more than a little awkward.

Guys, help me.  How the hell am I going to get these bikes de attached...from each other ?

It's a relatively cheap bike chain.  So it's covered in plasticky rubber stuff with a relatively cheap thin chain thing in the centre.

 What do I do here guys ?  Do I borrow some bolt cutters from somewhere ?  How about if I just try an axe....could that work ?  I'm not much of a toolshed man, so I'm looking for some assistance.  How would you break this bike chain and separate these bikes.  Do let me know.