plan in advance you shouldn't have any problem. Many WDW restaurants fill up early which makes it harder to fit in a party of eight. Plan early, book early and you should be okay.
You will likely see a note, or be told, that your party may be seated at separate tables. This is a standard disclaimer. Disney will work hard to get you close together.
Or you could book all of your meals at Biergarten. Their communal tables mostly seat eight.