I agree with MIJul.
7 1/4 square includes 4 whole stars - so quartered is a star on each triangle IF they were cut straigt (to the print). Because it's on an angle, some of your triangles will have a star on it, and some will have half or a quarter of a star (depending on how many rows you have to cut). I am inclined to think that for this size triangle you'd want to go with a smaller print - unless your intention was to have a perfect (or near perfect) star in each triangle. If that was your intention there is nothing to do but cut it straight to the print and buy more fabric if necessary.
Also ... when you get to the stripe fabric - definately cut that to the print, not the grain. Check it first and if it's off starch it heavily then cut it so the print is straight.