I briefly visited the Grand Californian on Tuesday. Currently, Condor Flats is walled off, and my understanding is that it will remain walled off during your trip. If so, that means that it is a fairly substantial walk from most of DCA to the entrance to the hotel that is in DCA, since you can't pass through the area that goes past Soarin'. Right now, you have to walk through the whole Grizzly Peak area and you come out near Ariel's Undersea Adventure in Paradise Pier. So if you want to do Hollywood Land for Frozen Fun or maybe even Cars Land, it's probably not much of a time savings to stay at the Grand Californian, even if you get a room in a convenient location to the parks. And I'm pretty sure that currently, you can't save any time/hassle by going from
Disneyland through DCA to the Grand Californian, but that it'd be faster to walk out of Disneyland through Downtown Disney, which is fine but not as magical to me as staying in the theme parks. (The walk to the Grand Californian through DCA is not UNPLEASANT, but it's not convenient and to my tired feet, anyway, it was not very short.)
They also appeared to be doing construction on one of the pools, I think it was, at about 1 PM. The noise was so loud that children walking past were covering their ears (and me too!). I imagine that if they booked any rooms in that area, it may have been difficult for those guests to nap.
My mom and I both commented that if we had stretched our budget to stay at the Grand Californian this trip, we would have been rather disappointed. It's a gorgeous hotel and I don't think I would have
regretted staying there, per se, but it wasn't the peaceful and convenient getaway it usually is, and I might have wished I hadn't splurged during this particular trip.
In your case, I would personally go with the Desert Inn and Suites (but if "walking distance" doesn't matter to you, I see no problem with Motel 6). No, the walk across the street to the Desert Inn and Suites is in no way "magical," but it very well may be more convenient and quicker.
If you do want to stay on property, then if you could get a good rate at the Disneyland Hotel or even the Paradise Pier, that might be a good idea. But if money is any sort of object, I personally wouldn't stay at the Grand Californian until the refurbishment walls are down by Soarin'. (Again, I don't think they'll be down for a while, but if I'm wrong, that might change my answer.)