Creatine is often a cause of cramping if your H20 intake is not high enough, particularly after you take it. Try to drink a minimum of 1-1.5 gallons of H20 a day, and at least a full liter during the hour after taking creatine (which is best taken post workout).
Also, you probably shouldn't even bother taking Deca if you're only going to take 100mg week. Why don't you just go with Oxandrolone if you're so concerned about sides?