Where is the Marriage mod that adds suitable mates and children for ALL Skyrim races , fixes the dang bugs in the ones that do EXIST?
Adding children to the other races is pretty much an impossible task from what I've read, which is why there are virtually no mods in existence that add elf, Argonian and Khajiit children. The closest people have gotten to adding beast race children is by scaling down the regular version of the race in question and then just using the child voice for them. There is a mod that adds a Khajiit child that I think can be adopted if you have Hearthfire, which was created using the regular Khajiit body as a base. Adding Redguard children probably wouldn't be too difficult, but the only thing is that they don't look like Redguards.

As far as elf children goes, one mod adds an orc child (I think it's called Adopt A Child, but I don't think the mod is currently being updated anymore), but that's the pretty much the end of it as far as I'm aware.
As far as marriage goes, any race can be added to the marriage options, but unfortunately, the Khajiit would have to use voice types other than their racial ones because they never recorded marriage dialogue for them, and probably never will. New lines could always be added in for them, but it would involve having to make edits to the marriage quests I believe, which would mean that the mod would end up incompatible with every marriage mod that also tries and edits the related quests. It's a little problematic for some of the other races as well, but I don't consider it to be nearly as bad.
As far as marriage mods go, http://skyrim.nexusmods.com/mods/searchresults/?name=marriage&order=DESC&orderby=date&page=1 are several on the Skyrim Nexus if you search "marriage," and http://skyrim.nexusmods.com/mods/8429 also adds some marriage options as well, but the latter doesn't add options for ALL races.