Hello E.-
I've studied child development for more than 16 years, and if there is one thing I've learned about children, they learn through play. They act out worries, concerns, questions through play, whether it's play with a friend or dolls. Children learn social cues through play and they learn cause & effect lessons through play.
Many recent studies lately have encouraged parents and caregivers to reduce the amount of structured lesson time in a child's day and allow them to play. In the past few generations, (1980's & 1990's), the focus was on structured lessons, piano, dance, science, math lessons along with organized sports. They are now finding that these structured activities, add stress to children, because they cannot do what is natural, free play.
So the answer to your question is yes, you can grow suscessful adults through play, because your children are learning important skills while playing.
R. Magby