Colorful, active and hardy!
Plus you should consider the level with which your selections occupy the water column, meaning you want fish that stay on the top of the tank, species that swim in the middle and species that stay in the bottom.
TOP LEVEL
Espei Rasbora - cool little top level schoolers with neat body patterns. Mine are very active and they are usually readily available.
Long Fin Leopard Danios - the long fins, cool leopard pattern and the "I'm all over the tank" attitude make them a really fun fish. I listed as top but they do go allover.
MIDDLE/BOTTOM
Rummy Nose Tetras - beautiful fish with red noses and checkered tails plus they are tight schoolers and stay together - mine are bottom to mid range swimmers and are Super Active- I love this species!
Cardinals - they are just beautiful and make great companions.
BOTTOM
Small group of cories (5-6)
A small Pleco: bristlenose, pitbull or my favorite "Pucallpa" Gold -- kids love catfish, grown ups too!
SNAIL
Nerite - cool patterns and its neat and easy to keep snails.
This is just as couple of suggestions, there are so many great species that will work well in as 29.
There is a chance your kids might lose interest, so pick out fish you like as well...
Have fun and be patient!