It does offer an interesting point. We don't really know if veela traits are capible of being passed down to male children. After all, it is Fleur, her mother, and her sister who are part veela. Maybe veelas can only have female children. Fleur's grandmother having Apolline might have been a fluke. We don't know how or if veela's reproduce.
Keep in mind we don't know how strong Veela heritage is, but Fleur, while beautiful, wasn't knocking men silly the way a full-blooded Veela does. Her children will be only one-eighth Veela. That will probably give them a certain amount of charm and natural good looks, but they're not going to be supernaturally attractive.