Datepicker / validated fields

I have a form including 2 datepicker fields (for a start and end date of a reservation period; datepicker_1 allows choice of dates from today onwards - datepicker_2 allows choice of dates from the selected datepicker_1 value onwards). On submission the entire form is validated and, if validation fails, the form is re-presented for correction. All validated field values are populated as you'd expect from the WAFV_Conditional values - except the datepicker fields.

How to I set the initial value of the datepicker fields (assuming they're validated) to the WAFV validated field value when the whole form is displayed, say, for other invalid fields to be corrected?

I know how to set the initial date, for instance, to be today (so earlier dates are not selected):
dateFormat: 'D, d M, yy', minDate: 0,

but can't figure out how to set the date, after validation, to a validated field being returned with all other WAFV_Conditional values.