Biggest mistake you can make here is going off too fast. Anything around half marathon pace for the first 5k is fine, definitely not quicker, then the sea wall and hills will naturally slow you down.
This is week 1 of the plan so no expectations here, no targets times and no reason to be disappointed, whatever happens, unless you throw the towel in completely.
90% of the field will walk at some stage in this race so if you do, take 30 seconds and then start running again.