Hi qwark2000,
You will need the horse to win to make profit on this offer. Try to keep your match losses to a minimum and you can get cash in with the free 50 bet.
I could be wrong but I think you can bet on the second or third race in the morning too. It’s your first bet on each market that counts towards the offer. But I suppose if you’re doing all the races what you’re doing is the right way to go about it given the possible profit! Best of luck.