While waiting for your Gi to shrink and experimenting with cold and then (if you need it) hot washes, you can roll the waistband to shorten the height of the pants. This works well with drawastring or elastic waist gi pants. Many children and women who have trouble fitting traditional sizes do this in my classes (children because they will grow and eventually fit, women while deciding how much to alter). I usually do this with my new gi's as I find the good 100% cotton ones shrink a full size in 2-3 washes so I roll the waistband until they shrink down to size fully.
