It really depends. What time of year (OK, June)? What day of the week? Is it a week where the shows are very day or only on weekends? Are there two Fantasmic shows that night? If so, which one will you attend? Are there two parades that day? If so, which one will you attend? How young are your children and how long can they sit and wait?
Without knowing anything more than what you said, I would say:
POD - at least 30 minutes early
Remember Dreams Come True - at least 45 minutes early (I would do 60 minutes to be safe)
Fantasmic 1st show - 90 minutes early
Fantasmic 2nd show - 30-40 minutes early