Hi,
Cramps can become more common (I usually get them while I'm lying down or asleep) but if you feel that they are getting really bad, you can buy some magnesium tablets from any pharmacist or fitness centre.
Magnesium is very good for preventing muscle cramp as any physio will tell you, and while you should be getting your full daily allowance of magnesium from the shakes, taking a supplement will not affect the diet in the any way.