Re: Video games
I think your plan sounds very reasonable. Is a Nintendo DSiXL something your kids could play on together when your DD gets older? If so, then I wouldn't worry about keeping other systems around for those cold days. In the mean time, could you make a rule that all of the Nintendo DSiXL equipment and games be stored in a bin in DS's closet, so DD can't get to it, and maybe have something special for just her to play with during the times he wants to pull it put to play with. Or could he even play with it in his room only, with the door shut? Then it is not a temptation for her.
Sorry if my suggestions don't make sense. I have no idea what a Nintendo DSiXL looks like or how it functions. We have 4 kids and have so far managed to avoid any and all video games. I dread when that day comes...