[Recurring events]

Yes. On the Add Event page, there is a field titled "repeat." Select "weekly" from the drop-down list and then pick the day (if it isn't already selected) and the end date and you are done.

Here is a link to our help topic with more details.

[Parent/Sub-calendar Question]

If you post the events that are in the subcalendars to the main calendar too you aren't increasing the chance of errors--I don't think--because you still have a single event showing up in two calendars. If you change the event in either the main calendar or the subcalendar, it will change it in both places. By posting an event to another calendar, you aren't making a copy in the other calendar. You are just having it show up in two places.