Go for main, your home time doesn't matter.
On ship the main dinner is at 5.45 ( some 6.15)
Kids that age can't eat late, they will hit the snack places and spoil their proper dinner.
I have seen too many melt downs at late dinner which runs 8.15 ( opening) ordering and getting good is layer and ends at 10 pm.
Bodies cycles normally start shutting down food processing in the evening, the old saying, eat breakfast like a king, eat lunch like a prince, eat dinner like a pauper.
Sugar levels return to normal quickly in a 12 hour cycle from breakfast to dinner, but eating late the body can't process it, sugar goes up and up for up to four hours post late eating.
With soda and snacks it will cause upset tummy.
You need to let good go down, dinner then show or club works, show then dinner is for adults and teens only.
On ship you will be up with the sunlight, eat breakfast at 7.30 to 10 am, - earlier if in port, lunch 13 noon to 1.30 pm, or off ship local time, so your body is on ship time, local home time doesn't matter, you can't go 1.30 pm to 8.30 serving time with young children.
They will eat eat snacks fast food and not be hungry at 8.30 pm.
We live in London, so on a cruise in the Caribbean , eating local home time, means eating at 1am, 7 am lunch and 1pm dinner, ( Alaska would be 11pm breakfast 5 am lunch, 11 am dinner? Sounds silly, children adapt to local time very quickly, avoid late dinner unless as a family you all eat at 8.30 pm at home or later.