I like Gentilly, too...that's why I've lived there since 1984 and raised my two teenaged sons there.
We live in Gentilly Terrace and Gardens, and there are a number of homes in the neighborhood that are now being renovated, we assume to place on the rental market. The neighborhood is a served by Gentilly Terrace Elementary, one of the UNO Charter Schools. Typical not-quite-but-almost suburban living; you have the houses on a little bigger lots, set back from the street with front yards...but many of the houses are California bungalows built in the 30's and 40's and you're also a short bus ride down Elysian Fields from the Quarter. And an even shorter bus ride out Elysian Fields to UNO...which my oldest son is now attending.
Marigny is a really nice historic neighborhood (New Orleans' first "suburb"), but it's probably a little more of an adult neighborhood with a bit of a "counter-culture" feel at this point in time. A lot of folks who might have liked to live in the Quarter but not at Quarter-type prices have found the next-best thing across Esplanade in the Marigny...and are now actually sort of extending further into Bywater. Like I said...nice neighborhoods, and I'm not going to say they are or aren't "child-friendly". I grew up in a neighborhood not too far from there myself. There's a lot to be said for growing up in a historic neighborhood near the heart of a city.