The NF1 Gene – Disclosure and Shiduchin

A young couple I am familiar with has a daughter who developed a brain tumor at the age of 3, which has unfortunately spread to the spine. They have three other children, including a son. During treatment they discovered that the child carried a mutation in the NF1 gene, which is responsible for neurofibromatosis. Upon further testing, it was discovered that one parent carried the same mutation. Other than a few brown spots this parent did not have any symptoms of the disease, not did anyone else in their immediate family.
Issues they have to address include whether to test the other children for the mutation, and what they should do as far as having future children. An additional question for the future will be what to do when it becomes time to do shidduchim with their children- do they tell the other side about this problem, even if the child does not have any symptoms?
Several medical professionals have recommended that they proceed with IVF together with pre-implantation genetic diagnosis. The family is a very erlicher kolel family living in Lakewood. They are looking for hashkafic and halachic guidance, but are unsure whom to contact. The situation is complicated by the unknown severity of the mutation. The particular mutation has not been previously found, and by some criteria can be considered a mild one. Although one child is seriously ill, the parent and other children do not have any symptoms.
Is there a consensus about what the proper approach should be in such a case, particularly  in regards to NF1? Also, can you recommend a local Rav with is knowledgeable in these inyanim who can provide halachic and hashkafic guidance to this family, now and in the future?
I thank you for your time, and am looking forward to your response.