Sean,
You should create individual webinar programs for each session for tracking purposes (simply create the first one as a "template", clone it and replace with the correct dates and times), but as far as the registration page, it's fairly simple to do.
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If you only want them to select one, create one custom field, or if they can select multiple dates, create the correct number custom fields (I would name them something generic so you can reuse them easily, like "Webinar Choice 1", "Form Choice 2", etc.)
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Add the field(s) to the form.
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In your smart campaign in the parent program, you can use a flow step to send peple to the correct program based on the field values.
There are a number of threads in the community about this, a quick search should turn up some more detailed answers.