Hello. You can do just about anything with our custom fields. You could setup the regular price full week, then make a custom field where the user could mark if they are only coming half-day. If they select that field, then it could discount $10.
You could also setup custom fields to select any workshops during the event. If needed, additional fees can be added based on which workshops are selected.
If you have users login to your site, then their event registrations will be associated with their user accounts. THEN, they'd have the ability to access our frontend user panel where users can make changes to their registration, additional payments, cancel, etc. You setup what is allowed in the user panel.
In the user panel, users could change the workshops they are signed up for, add some, remove some, etc. They would only have to pay if the changes they make calculate to a higher priced registration than what they already paid for. You can also add a "change fee" if you wanted to.
With this user panel, users would be able to see everything they have registered for, when they registered, how much they paid, how much they owe, etc.
If you have other questions, let us know.
Nathan