Artista is right there in the same building, but it will probably be packed afterwards.
Downtown Aquarium is certainly convenient, but I should probably have my chowhound access revoked if I recommend it. If you're ok with overpriced, mediocre food, and are ok with having your niece being the only one who enjoys it, go right ahead.
The restaurants at Bayou Place are also not great.
Those places probably deplete the options that are easily walkable. Closer to Main Street, you have quite a few more options, including Voice and Azuma (sushi).
If you don't mind driving a bit 2 miles, Midtown has a few more options. Reef is excellent, Farrago is pretty good as well.