Don't know if there's any money to be used... You might find one of the suppliers of the resources you use has the ability to come and give a talk. Some may charge though. This might be a company involved with literacy or maths (e.g. Numicon). Or you might find an independent practitioner who for a fee would give a talk (e.g. physiotherapist, occupational therapist, speech & language therapist etc.) as many of the youngsters are likely to have a variety of problems not just one. Or a local college might admit school leavers and staff would come and outline what they can do. Or try the national charities for the main learning difficulties and see if they know of anyone prepared to give a talk.