What are the ages of the kids? Are they interested in the characters? Your two options are totally different.
'Ohana is darker, more exotic. There's plenty of food but it is what it is (no choices.) DH & DS13 LOVED it!!! But they are good eaters so they got their monies worth. I thought it was good, but just so much & it just kept coming. DD8, not a great eater, ate a little of the chicken & some noodles, but that was about it. The service seemed rushed & the "cousin" bit got a little old (to me--kids thought it was funny.) DD wasn't interested in joining in on the parade. We were seated far away from the main entertainment which was fine with us. We would not do it again mainly due to the $$$, but glad we tried it once. If we did a DP, it would be a good use of a TS credit though.
1900 is light, bright & a fun atmosphere. The food is typical American dinner buffet so nothing too exciting (except the yummy strawberry soup!) DD5 (at the time) ate up the character interaction! The step sisters are quite funny. There is a parade for the kids & DD happily joined in on that. It's definitely more chaotic with the characters moving around and there are more families at 1900 than 'Ohana.
Either way you can ride the monorail to the resort which our kids love. Consider what it is you're loooking to get out of the meal. For the "experience" 'Ohana is very nice. But for the "EXPERIENCE" 1900 offers that with the characters. It may come down to where you can get an ADR that fits your schedule.