Fill in Flash (before the reshoot)

I am going to Branston Waterpark tomorrow to take some more pictures using fill in flash (and some others) while I am there. I have got all the items I set out to get myself to try and improve the shots I get. I am hoping that with what I have learnt that I maybe able to use some of the shots I get for my final portfolio. Also I have got myself a new lens to play with that should also get me closer to the subjects as it has a zoom of 400mm and my existing lens only went to 300mm.