Even Tate Modern.

They'll get tired and not enjoy it and start screaming.

Wait till they're old enough to not uncontrollably scream.

Alternatively, tie them to the raillings outside or leave them in one of the poster drawers in the gift shop.

Remember that chucking your beans up each other and subsequently clunge-plopping a smelly little ball of semi-you does not give you license to fuck my Sunday in the arse.