Yes, absolutely! The buses run for at least an hour after Illuminations - you won't get stranded.
Consider asking the captain to drop you off at the International Gateway dock - that will be a shorter walk. When we did the Illuminations Cruise, our captain did that for the family we were sharing the cruise with. I got the impression that they really weren't supposed to do that, though, so you may get a polite refusal to your request (but I'm pretty sure it will be all right).
If you are in a hurry, it's easy to get a cab from the Boardwalk. You could be back at OKW in 10 -15 minutes for about $15, including a tip for the driver.
Another option is to take the DD bus from the Boardwalk and transfer to the OKW bus there. This would be fun if you wanted to spend a little time at DD before you return to your resort.
Enjoy - the cruise is awesome!