Oh yes, I can definitely recommend someone!! There's a company whose website is
www.nuttyschildrensparties.co.uk who offer all sorts of adventure/ games style parties. All the entertainers are actors or actresses and there's one in particular called Sophie who is fantastic. I have a personal interest as she was my next door neighbour for 13 years and I've watched her go through school, university and now into her career but you couldn't hope to meet a more genuinely amazing young woman. She's brilliant with the children and her enthusiasm is infectious. Your son will adore her, as all three of my children do, especially my six year old son who begs me to let her look after him!
Hope you get something sorted for the party and good luck with all those 5 year olds.