I think this is an excellent question! I like to think positively... so here are the pre-children positives IMHO...
-late nights at the parks, enjoying rides, fireworks, etc...
-sleeping in and taking your time, never much need to rush anywhere...
-nice meals in relative peace and quiet, just the two of you...
-rides, rides and more rides (if that is your thing, it is mine

)
-a romantic, leisurely stroll through the EPCOT World Showcase at night
I am sure there are many many more! And I see from your OP you enjoy many of these activities as well...
The post-children (we have a DD5 and DS3 who have both been twice and we are going again in Dec.) positives, IMHO, are many too..
-early mornings at the parks, enjoying your kids enjoying their rides...
-naps and/or down time at your resort and pool, which really makes you appreciate staying onsite
-fun meals, including the character meals, where you can be a kid with your kid
-parades, shows and character meets, oh my...
-visiting each and every country in the World Showcase with your 4 year old to get her mask decorated. (We had never set foot in some of the buildings in many couples trips, so it was pretty cool to see some new sites!)
And of course, the most important post-children positive, having someone to share your Disney obsession, no questions asked! It is so much fun, passing my love of all things Disney to my kids! Seeing the "World" through their eyes is truly special!
So thank you, vettechick99, for asking and making me appreciate my children that much more!