How many Nanny’s do I need?

For the safety of the children and so they can have the best time and get plenty attention on the big day. 

I work on these ratios 0-3 months 1 event nanny per baby. 

3 months - 5 years 1 event nanny to 3 children. 

5 - 12 years 1 event nanny to 4 children.