For $160,000, you can hire a private jet for London - LAX return which is a similar trip length to that of London to San Francisco. This aircraft seats 13 making the trip approximately $12,300 each if you could find 12 other people to share it with. That's a similar price to paying for fully flexible first class.
For that you typically get a private terminal, minimal security, ability to take almost as much luggage as you wish, and an aircraft that will wait for you and take off whenever you want. You also guarantee to be sharing the aircraft with people of your choice.
The OP specifically asks "how to avoid toddlers". This question and similar questions, such as how do I avoid drunks, people who snore or sitting next to someone with bad body odor, or why should babies be allowed in first class, typically end up with the canonical answer that you should fly in a private jet. When you are taking a form of public transport, inevitably you are going to come across a disagreeable situation or disagreeable passengers.
On almost any airline (apart from, I think, one exception), babies and young children are allowed in all cabins including First and Business class. Children under a certain age are not allowed in the exit row, but they are allowed in front of, behind and in the bulkhead adjacent to the exit row. There are many parents who can afford to travel in Business and First and you see young children in these every day. Some parents prefer an overnight flight to a day flight in order to get the children to sleep more quickly. In summary, you can almost never be guaranteed to more than one seat away from a toddler.
If the OP had said he'd had an uncomfortable flight and asked what's the best way with dealing with noise on an aircraft, I would have provided an answer responding to that question, rather than the question that the OP did ask.