When doing estate planning with an heir who has special needs, you really need to take the time to carefully consider what can be most helpful to them when you are gone. Careful advance planning is the key. If you do it correctly, your assets can change their life, but you have to remember that this all falls on your shoulders. You need to make the proper decisions at the proper time.
Often, this means doing things well in advance. You do not want to take any risks with putting estate planning off until a later date. If you planned to create a special needs trust and never got around to actually doing it, and then you pass away in an unfortunate accident, the ramifications for your heir can be dramatic. For instance, will the money they inherit directly -- without a trust to manage it -- make it so that they cannot get government assistance? It's something you want to think about.
Doing the planning in advance, though, also means you may have to come back and update it. Your heir may require different things at different ages. For instance, learning disabilities often get diagnosed far later than other types of special needs. They simply do not show up in young children who are still developing anyway. When the kids get older and it's clear that they are falling behind their peers, that's when the full scope of the disability makes itself clear.
Since planning is so important at every stage in life, it's crucial that you know exactly what steps you need to take.