I might try to aim for about that amount, then; and even if it's a little on the high end, it's better to aim too high than to aim to low and have nothing to offer, maybe?
For the bonus stuff, how long after Inksgiving do you think people expect that bonus content? I would want to maybe do both bonus content and unlocking extra episodes, but I also tend to be a little slow and my life is hectic right now, so I don't want to disappoint people by taking too long to deliver.
If you decide to do something, maybe you could put together a list of prompts and have people vote for their favorite ones?
But yeah, it's definitely a fun event from the sound of it! I learned about it from reading people's comics and seeing their Inksgiving announcements and whatnot--so it got me excited for when the next formal Inksgiving would come around.