Let's see now... if you remember, in Mario Party 1, there's a "Peach's Birthday Cake", most likely meaning that it was Peach's birthday. Correct me if I'm wrong, but MP1 was released on Februrary 12th. Peach looked about 9 in October 1985, causing her to be born in 1976, and Therefore, Peach was born Februrary 12th, 1976, causing Peach to be 25.
Super Mario Land was released in 1987, right? Daisy looked to be about 15-16 in that. Therefore, she was born about 1972, causing Daisy to be in her late twenties, early thirties.