This is certainly an area that we have looked at, but a Henson Trust is complicated. It has to be custom written for each need, depending on the care required, and the financial assistance already being provided for the child. It's a sophisticated trust that doesn't lend itself very well to an online interactive service like ours.
If you have a child with special needs, and feel that you need to set up a Henson Trust for them. We would recommend that you seek legal advice, and have the trust drafted by an estate planning professional.