What to do for my 13 year old sisters birthday party and my 11th?

her birthday is July 23 and i want to get her something also my older sister("adult" figure my parents died 6 years ago) is having trouble to find a theme my sister and i are Amish as our therapist put it so ya we will have a total of 6 girls me her 2 of my friends 2 of hers(both of our birthdays are around the same time so we make it one birthday) so ya what can we do for our birthday party