I've never done it myself, but I think household names with a space in them require quotation marks for the money cheats to work (so it'd be something like: familyfunds "fortin kids" 10000). I don't think it should be taking money from the old household at all, though, so I'm not sure why they're broke.
If familyfunds isn't working no matter how you do it you can always use the cheat 'motherlode'. It's a flat 50k simoleons each time you enter it.