See I disagree, I think any vacation is what you make of it. I research everything to death so I'm knowledgeable but don't go with a commando style of touring. I like to know my options and then as a family we each choose a couple must sees and we make sure to find time for those things, everything else is just gravy on top. You will never see all and do all at Disney with our without a baby in tow. Just be sure to know what’s up and be flexible, if the kids (even the 6 y/o) need a break, go back to the hotel for a nap or find a park bench to sit on and just people watch, do a show, what ever floats your boat.
And I think a 9 mo old is better than a toddler b/c toddlers are mobile, a 9 mo old is usually still portable (mine did walk days before turning 9 months old but still would sit in the stroller so if we went places I didn’t have to play chase).