Theoretically you just turn up at the restaurant and they'll find you a table. You might have to wait a little longer if you just want one for both of you. With Thomson's running the Island escape now, that's how it worked on there. We never had to wait more than a few minutes for a table.
And you'd be fine going with just you and hubby. If we'd have waited to try and round up the boys for dinner we'd have starved to death
Also as an alternative to the Orion restaurant you could consider the A la Carte Grill for the 2 of you.
And I know it's buffet, but Sirens has tables for two also.
We'll be on board in April and I'll be reporting back ASAP on our return.