I think maybe the potty training and dreams may be two different things. my son had "night terrors" around that age.
Have you tried chocolate? The mini ones? we kept them in the bathroom and everytime my husband and I went, we said, good mommy, good daddy, and we took a chocolat. we kept it out of reach of my son so this was before he even was potty trained. He was ready but wouldn't go on the potty. After a couple of days of us eating chocolates for going potty (husband and I) my son got so frusterated he sat on the potty and peed and said "good boy, chocolate"? so after that every time we kept reminding him, "do you have to go potty"? and he would remember the chocolate and go potty. We only gave him one if he went potty. Was a great incentive, someone else told me about it. We only needed to use them for about a month and then "good boy" was sufficient. Now he goes totally on his own and hardly ever has accidents.