If you're counting values per day, you're missing the Calendar table. If you left join the Calendar table to the table of scheduled events, then it's stupid easy. You need all the days between these two dates:

SELECT MIN(Arrival_Date) AS FirstDate

,MAX(Arrival_Date) AS LastDate

FROM [wce_bookings];

Then you join your Calendar table to this.

SELECT c.Date, b.BookingID

FROM Calendar c LEFT JOIN Booking b ON c.CalendarDate BETWEEN b.StartDate and b.EndDate

then you can just count them