Depending on your breast size, you can also just carry baby at breast level. That's how I carry my little one in a front carry (in either a mei tai or wrap) to be able to nurse as needed. You then just simply raise or lower your top and nurse upright.
If you aren't able to carry baby at breast level, then yep, just lowering the mei tai a little, by undoing the shoulder straps (don't need to lower the waist straps to nurse) and retying, will work.
