This takes a bit of work but it’s pretty simple and straightforward. And if you position it correctly, it works year round, too.
Become an Amazon affiliate. Now search Amazon for the best toys for kids. It could be for a certain age of kids, or a certain type of toy (like educational) or whatever you choose. If Halloween is coming, you can do the best kids costumes. For Christmas it will be the best presents for kids, and year round it can be the most popular, or educational, or most fun, or whatever criteria you choose.
Build a page with each toy listed. Give each toy a fun description and a good picture.
Under each toy and description, put a “click here for more information” link. This is of course your affiliate link.
Now haunt the mommy forums and sign up with a woman’s name (yes, even if you are a man.) Find the busiest threads, leave comments, and mention where you got some great present ideas for your kids. Give out your link.
I know for a fact this works. You won’t get rich, but you will make some extra money. And you can always outsource the forum comments to someone else to perform for you.