I don't know a lot about this topic. I never went to one of those convention type workshops. I also never participated in an online one--but I assume they have the advantage of not costing money. And, I never took a writing course. I taught one once, and it was pretty much useless. I'm not sure you can be taught to write--possibly a course or workshop may provide a few insights or useful tricks, but I think it's usually something one has to teach oneself. Plus you need talent or native ability, and the capacity to look at your own work objectively. Most people I've run into who express a desire to write and publish turn out not to have read widely or analytically--and most of them haven't written a lot either, or cultivated a critical eye. I suppose my stock advice to someone in your position would be to read your way through the children's department of a good library, finding books you admire and trying to understand their structure and the technique employed, and also to write a great deal, and critique your own work vigorously. Actually getting the stuff published is quite hard and a study in itself--there are probably thousands of websites that discuss strategies. Or...you can take what you already have, self-publish, or employ one of the print-on-demand publishers, and give the books away as Christmas presents. Would probably cost no more than going to one or two of those conferences.