Hi James, You can ask the guests to add this information to the Booking Notes field on the checkout page. For this, you can change the text of the label ‘Notes’ into ‘when they are likely to arrive’. You can do this by editing translations of the plugin. You can use a free third-party Loco Translate plugin for this. Or you can use Checkout Fields Editor add-on to add special field(s) and collect additional information like this.
OK, I had a play with Loco Translate and had no idea what I was doing. I found Notes: But changing it made no difference to the booking form. So I looked at your plug in, and it costs almost as much as the theme!