I want to distribute my assets among my children during my lifetime, is this permissible?

I am not clear why you want to do this. Do you want to give them to your children as a gift, distribute your assets during your lifetime, or write a will? Each of these situations has a different outcome. Suppose you have 100,000 riyals, or 100,000 of the currency of your country, and you want to divide it among your children as a gift. You have to give them each an equal amount, without making any distinction between sons and daughters. All take equally. This is because children have the same rights to upbringing and education. Parents must not favor any child of theirs over another, for any reason. When a child has special needs, as in the case of a child suffering physical or mental disability, the parents must provide for him or her in accordance with their means and in a way that maintains fairness among children.
It is wrong to divide your money in accordance with the rules of inheritance while you are still alive. This is because you do not know who of your children will be alive when you die. We should always leave the inheritance to be determined by God's law, as He intended it. On the other hand, if you live in a non-Muslim country and you need to draw a will to ensure that your children receive their shares in accordance with Islamic law, you can do this by specifying their percentages, rather than by giving exact figures.