I don't know but you should go to your SMT/Governers and ask if they have a policy regarding this. They run the school, they are libel for any legal ramifications. If the Governors dcide that you can slect for school trips based on disability then go with it. If they say that no child should be excluded from a trip then find somewhere else to take them allor cancel the trip. Either way it is the Governor's decision not yours. Have you spoken to the venue yet? It may be thast the sentence on their website is a backside covering exercise because of a specific problem they had with one school.