Where the shirt is baggy will be under the vest anyway, so that's not a problem. The pant legs may need to be taken in just a little though. How you do that is to turn them inside out and put them on, then pinch it on the inside seam at the knee until it's loose but still close to the body (only JUST loose enough that you could slide a 1" dowel or a typical lightsaber blade up inside). Hold that pinch and mark with a piece of chalk. Then, lay the pants flat on a table and draw a straight line from the chalk mark to the bottom hem, and a curved line tapering in from the knee mark to the crotch (curved so that there won't be any weird bulges when you sew it and turn it right side out again). make an identically spaced line on the other leg, and then sew a new inside seam on those lines.