Time for guests to arrive?

Does anyone else have a situation where their guests need to travel into the ceremony site once they arrive to a location? We are having our ceremony at a farm property at the edge of their property, which requires guests to take a horse and wagon to get back there (about 8 mins). Is there a way to word on the invitations "you need to get here by 2:30 even though ceremony doesn't start until 3 because you have to have travel time once arrived"? Only 30 guests can go at a time (we have about 80) so trying to figure out if there's a way to communicate that they need to arrive earlier than ceremony start time because there will be additional travel time....and how to ensure all the guests don't show up 10 mins prior expecting to all get back there at the same time