My comments in
bold & italicize
MK night 1
- Liberty Tree Tavern
This sounds good, depending on what time you arrive at the resort and how far you've traveled.
HS:
- fantasmic dining - 50s Prime Time
(not too excited about the restaurant, but buying it for fantasmic seats for our young kids. worth it? Or just do quick service at docking bay?)
I would do quick service at docking bay and get seats for free, if you're willing to line up for them early (I believe you can line up 90 minutes early, but unless you really care where you sit, you should be okay 30 minutes before the show).
Resort day:
- considering GF Cafe for breakfast, or just Poly quick service, or making the trip to Boma (worth the travel on a resort day?)
- slightly considering Storybook for dinner or just staying at Poly. Really wanted hoop Dee doo, but they are closed on Mondays and Tuesdays.
You're at the Poly. Their quick service - Captain Cook's - is pretty ok. If you drink coffee or soft drinks, I suggest at least one or two refillable mugs for your family of 6 and sharing.
Epcot:
- Garden grill
Never eaten here, so no comments
AK
- none (Quick service only)
MK final day/night:
- Bibbidi Bobbidi Boutique (assuming won’t be able to get reservation on first MK day)
- Cinderella’s Royal Table
- this one is tough - we are staying for Happily Ever After on our final night, but not our first night. Is the post-fireworks dessert party worth it for a four year old and six year old? Should we do that instead of CRT or LTT?
Worth it is subjective, so it depends on what you want for your money. A nice area to stand in or dessert. There's a nice area to stand in (sit for a while, til they tell you it's time to stand up). if you can manage to be at the front, where the grass meets the little fences, then yes, it's a great area 
I would try for HEA on the first night, again, depending on what time you get there, but not as a dessert party.
Departure day:
Topolino’s
If you do HEA on your final night, then I wouldn't plan anything other than a quick service breakfast. If you must do Topolino's, consider going to do this on your resort day and doing the Poly quick service on departure day.
