Clarifications
I read a couple of remarks on here I think are either out and out wrong, or require clarification.
One mentioned who can or can't be an executor, my understanding is that anyone over the age of 18 can be an executor regardless of whether or not they're a beneficary. My understanding is based on the fact, I've actually assisted many people in this situation. As to the validity of the Will, I thought to some extend that was the purpose of probate, but regardless, I don't believe it's the Executor's duty to assume a Will is going to be challenged until such time that it is.
Compensation. My understanding is the maximum amount is 5% of the estate, but you still have to justify whatever it is you wish to be compensated or it could be challenged. If you want closer to the maxiumum amount you're entitled to the estate has to be complex enough to warrant that amount of remuneration. Also if you're a beneficary and an executor, you can still be paid for the work as an executor, but it's taxable income. I also believe the estate has to issue you a T4 and it has to pay of all things, EI and potentially CPP.
Any executor should probaby apply for a clearance certificate if there's any possibility that the deceased has not paid taxes in prior years. The clearance certificate relieves the executor of this potential tax burden.
As for the question of a disabled child and government entitlements, most estate planning options centre around a Henson trust, with is essentially a discretionary trust. I believe one can allocate up to $200K into that account and it's not considered an asset for GAIN benefits. (I haven't reviewed this in a few years so the GAIN name could have changed), meaning a disabled individual could still be entitled for full benefits.
As for someone who doesn't necessarly want to treat family members equal, how about gifting things prior to death, it seems to me that would be the most practical way of dealing with it. Or have some life insurance with the beneficaries you wish to give preferential treatment to. In otherwords, if you do want to treat family members differently, it's best to do so while you're alive and then hopefully avoid to the whole issue of being unfair in your Will. And as for the life insurance, that's on an estate asset, so it again avoids the issue of unfairness.
Anyway that's my 2 cents worth.