There's an option you may not have considered (and I know this is a heretical suggestion on HN):

Get a job at an established company doing this. If your product was independently developed in your spare time and in an area that has other companies in it you're probably the sort of person that other people who have money want to hire. There are developer jobs out there that pay $100k a year. It's likely more than you'll make with your startup and might give you more time with your kid rather than working current job + part-time at night. It might also be less stressful and eliminate concerns about taxes/incorporation, etc. There's a boom on right now for talent with a demonstrated interest. You might want to consider taking advantage of it.