Recently, I came across an FAQ for young parents and this question came up. The answer is a resounding yes, because if you don't have a Will and something happens to you, you have no say in who ends up taking care of your children and the Court has more involvement in that decision than you may really want.
You may also want a Trust set up so that you can control how your children will be taken care of financially, and ensure that they don't end up blowing any inheritance you leave them as soon as they turn 18. If you are wondering whether or not this really matters, ask yourself if you would give your child your retirement nest egg to invest at age 18 with no supervision. If the answer is no, then why would you give it to them without any strings attached if you weren't here to take care of them?
The point here is that estate planning tools such as Wills and Trusts are there to protect your children and give you piece of mind. If something unexpected occurs and your kids aren't protected, the result can be catastrophic.