Petition Disabilty card for disabled children

I would like the Government to introduce a card for disabled children to enable them to enjoy this countries fabulous historical and cultural places. Very often disabled children find it hard to cope with places like National Trust properties etc. and feel the need to leave quickly, whether it be because of boredom or mental/physical problems. A card to prove they have a disability and to enable them to have cheaper entrance fees to establishments could open up a whole new world to these youngsters, with parents not having to drag them round, disturbing other people, because "they've paid for it".