I have picked my two favourite invites, one for a boy and one for a girl =) Photo's and links are below. Both are personalised and printed off from your own printer.
Gorgeous pink invites from Freshly Squeezed Cards
Blue with chevrons from As You Wish Creations
You can make your own tissue pom pom decorations in blue, pink or whichever colour you are using. These look so effective and are quick and cheap to make! The tutorial is here
Here are some of my favourite examples of prince/princess/royal themed food from the interweb =)
Princess finger food from Kara's Party Ideas
Prince sweetie centerpiece also from Kara's Party Ideas
Crown sandwiches from Betty Crocker
Here is a link to a fab free printable! Use it to make your own cute favor boxes. Just add a thank you note and some sweets/treats and you are good to go =)
Free printable here
As always let me know if you try any of these ideas or if you have any suggestions for future themes!