To some extent, you can't prevent drama. People can challenge anything just likey they can sue someone for just about anything. It doesn't mean they will be successful, but it does mean a headache and probably legal expenses for everyone.
If you have greedy, drama-prone, or otherwise selfish/self-involved people in your life, you can't change that.
In addition to getting a solid will done by a legal expert, I'd say that being clear upfront with everyone helps, especially if there are surprises or unusual circumstances. In your life, that might mean being very clear with the partner and the Ex where your money is going, as well as to whoever will care for the kids (guessing the Ex?) and in what form they will receive that money (with what legal strings).
Also, let everyone know who will be named executor.
If there are special pieces, let everyone know that Timmy gets grandma's wedding ring and Susie gets the not-valuable but sentimental blue photo album. And name those things in your will if possible, or at the very least in a document notarized and left in place where everyone can access it and no one an hide it.
It seems like much of the time, drama is over minor things, like someone pillaging the contents of the house, not about challenging the $100,000 left to cousin Al. If you anticipate drama, having a thorough home inventory could help, but would on go so far.
My parents have been very clear. There are a few pieces designate for my sister and me. We both know where the documents are. Mom went so far as to drive my bk the bank branch that holds their safety deposit box (though the address is also listed in their documents). We know my sister will be executor. We know it's a 50/50 split, and very approximately how much that is. All of that will help prevent drama, but frankly, what will hopefully prevent most drama is just that I think my sister and I are both reasonable people, neither of whom will look to nickle and dime one another.