The Incas were a tribe traced to Peru in the 1300s. Though their capital city was Cuzco, Peru, the Incas eventually extended their empire to cover parts of Chile, Bolivia and Argentina. Inca garb was usually neutral, but adorned with colorful, intricate patterns of bright yellows, reds, oranges and greens in belts or capes. Clothing was usually made from alpaca wool, and costumes differed between gender. Chances are you won't be using real alpaca wool in your child's Inca costume, but there are alternatives to the material that you could use in your child's look.
Cut the sleeves and collar off a man's shirt in a neutral color such as black, brown or beige. Put this shirt on your son. If the shirt is too long, cut the bottom so that it skims the tops of your child's thighs. Don't worry about frayed edges after cutting because this will give the tunic a more authentic look.
Cut three long strips of cotton fabric in three different bright colors such as yellow, orange and red. The strips should each measure 4 inches wide by 4 feet long. Lay these three strips on top of one another and glue them together at one end using a glue gun. Wait for the glue to dry, then braid the length of the strips until you reach the opposite end. Hot glue this end and wait for the glue to dry. Wrap this braided belt around your son's waist and tie in the front, completing the tunic look.
Measure the length of your son's waist with a measuring tape. Using a pencil, apply this measurement to a piece of faux suede fabric, adding 6 inches to your measurement. Measure the distance between your son's waist and knees. Apply this measurement to the fabric. You should now have a rectangle. Cut out this rectangle and wrap it around your son's waist. There should be some overlap with the fabric when wrapped around. Pin near the upper waist portion of the fabric where it overlaps using an over-size safety pin to create a "loin cloth" that sufficiently covers your son at school under his tunic.
Have your son step into a pair of leather or faux leather sandals; Inca men usually wore animal hide sandals. To "age" your sandals and give them a more authentic look, leave them out in the sun for a few days to be exposed to the elements.
Put a black man's shirt on your daughter. Choose a shirt that is long enough to cover more than halfway between her knees and ankles, since Inca women typically often wore long black dresses that reached their ankles. Remove the shirt from your daughter, and cut off the sleeves and collar. Put the shirt back on your daughter.
Repeat Step 2 from the Boys' Costume section to create a colorful ornamental sash your daughter can tie around her waist.
Use a small micro-fleece blanket as a cape for your daughter's shoulders. Choose one that won't drag on the ground. Lay the blanket on a flat surface. Cut 1-inch-by-1-inch squares from cotton fabric in bright, bold colors such as red, yellow, green, orange and purple. Arrange these squares randomly, side to side, on the flat blanket. Create row after row of squares until the blanket's surface is covered. Hot glue each square to the blanket. Allow the glue to dry. Drape the blanket over your daughter's shoulders with the colorful squares side facing out.
Repeat Step 4 from the Boys' Costume section.
Part your daughter's hair down the middle and allow it to hang behind the shoulders, which was the way Inca women wore their hair.