Can a VBO form be integrated with the Commerce Add-to-Cart form to allow adding optional add-on products with checkboxes?
You could do it with Custom Line Item Fields for checkboxes and either just track the add on products using the line item or create a rule that adds the matching product to the cart when an line item is added that has checkbox field values.

PS: If you go with line item fields only approach, you should use pricing rules to change the final price of any line item with those check boxes to add prices to them. If you do that, then you might want this patch that allows line item fields to automatically ajax update the price when something changes:

https://www.drupal.org/node/1541886