I have 2 JQuery Date fields
Arrival date must not be todays date - i got this sorted using minDate: 1 in the javascr
I'm sure this example isn't perfect, but here's a working demo with most of what you require, using just jQuery and the jQuery UI Datepicker:
Datepicker & Difference Departure Arrival Nights
Play around with that and see if you can integrate something similar into your app/site.