SURPRISE PARTY!

I am planning a 13th surprise party for my best friend! I have no clue what do as the theme! I am having 9 kids including including me and her! I am keeping it very small! it will b the first week in feb. So it has 2 be inside! I am not sure If I should do it at my house small or at a bowling place and big! If it is at my house I have a way to get her there! PLEEZ HELP! she has always wanted a surprise party and I want 2 make it the bets party that she will always remember!