Booking online is only advisable if the tour date is not set in stone. Since Pelican Bar is literally out in the sea, it won't be open on days of high wave action. Make sure the date is flexible.
If not, you won't have an issue finding a tour operator at the last minute. Just make sure that they are a legal, licensed and insured red plated vehicle. All the drivers in our Transport section we know personally and all are legally licensed.