Our youngest were 12 months when they first went to WDW, but not because we didn't want to take them earlier, it just never happened. We did a lot of traveling earlier that year.
7 months old we took them on a one week cruise~came back and stayed in Ft. Lauderdale for a week doing the zoo, Vizcaya , etc. Then we went to the keys for 3 weeks!!! They had a great time even though they were young.
Then 5 months later we all got to go to WDW for the first time

We stayed for a week, drove to port canaveral and did another cruise for a week , then came back and did Disney for another week.
They had a busy year
I wouldn't "wait" until the kids are a certain age. I would wait until I felt like they would handle it okay. It makes me so sad seeing all these newborns in the middle of the summer with no hats, etc. burning under the sun and so miserable they can't even open their eyes

No~I wouldn't take a really young baby. I don't think it would be fair to them.
But even at a few months it would be fine. Yes it is more difficult and time consuming with kids~we have twins too~but it is wherever you go and it is so worth it!!!
I would say if you feel comfortable doing it~go for it! There is no right or wrong age
