That’s a tough situation since it’s so hard to predict how big you need to make the dress for it too fit. I admire you for taking on this challange! I think fitting the bodice with large darts is a good idea so you can decrease the size of the darts when the time comes. As for the waist, I’m really hoping that your pattern has an indication on where the waistline is. I would use the pivot method we demonstrate on increasing the hipline for increasing this waistline. Your first pivot point will be at the seam allowance intersection points at the top of the skirt pattern. I think this will be better because your increase line will go all the way to the bottom of the dress, which probably isn’t a bad idea in this case. As far as how much to increase it, that I can’t tell you. Congratulations! 😀