Robert:
You certainly can make
Advanced Dining Reservations without a resort reservation at the 180-day-out mark. Using the My Disney Experience link under your account at www.disneyworld.com, you can link up your dining reservations later simply by adding your dining confirmation number. (If you book online, your dining reservations will automatically show up in your account.)
The perk to booking your resort reservation prior to your dining reservations is to get access to making dining reservations farther than the 180-days-out limit. When you have a dining reservation linked to your account, you are allowed to begin making dining reservations from 180-days out of your arrival date
and an additional 10 days
into your vacation. This why some guests may check for a coveted dining reservation 180-days-out for Chef Mickey's but there are none. Guests who already booked their Disney hotel were able to book farther out than those staying off property or hadn't made their hotel reservations yet.
May will be here before you know it, so don't waste any time booking if you have a special location in mind for your family.
Wishing y'all a magical vacation!
Whitney