One of the worry-free ways to download an iCal file of all the upcoming events listed on your website is through the iCal plugin.
Import Events to Google Calendar
In an era where we all are preoccupied, Google calendar is the handiest calendar to make us remind everything, be it events or special dates. This plugin enables the users to let google calendar remind its users of all the events, by just importing the iCal file on it. Once, you download this add-on you can import all your events to your Google Calendar.