Hello Danielle,
Thanks for sailing by! Disney Cruise Line will actually do its best to match similar dining groups together, and therefore, adults sailing with no children are generally paired with other adults, and families will be seated with other families. It is highly likely, therefore, that your request will be met with no effort on your part. However, I recommend that after your book your Disney Cruise Line voyage that you call (800) 951-3532 and make your
specific dining preferences, so that every effort is made to accommodate your request. My family, like yours has dined alone and with other passengers, and have thoroughly enjoyed both. We still keep in regular contact with some of the families we have shared our wonderful Disney Cruise Line dinners with years after we disembarked. Regarding whether changing your dining table after once onboard, you could certainly make the request if you chose to do so, and the crew members will work to accommodate you. In this case, changes might be more difficult once table assignments are made, however, again, in my experience Disney Cruise Line will work to accommodate passenger requests. When you embark, there will be a time and location in your Personal Navigator that provides information on how to make table change requests.
I hope you have a wonderful trip!