Trust me on this one: Disneyland Hotel.
We have stayed at the DLH many times in the past and cannot use words to describe how awesome it is. Fresh and new and yet vintage and classic all at the same time.
We have a DS10 and he cannot get enough of the amazing pool at the DLH - honestly there might not be a better pool around for miles. And the food options are pretty amazing - Goofy's Kitchen for one of the best character meals on property (the PB&J pizza is our kids fave!), Tangaroa Terrace for quick service, Steakhouse 55 for a wonderful sit-down meal and Trader Sam's is a tiki bar with live Hawaiian theme music.
As for the Grand Californian, we stayed there in August for 5 nights with our son's grammy, who - full disclosure - paid for the rooms so we thought, hey we're not paying for it let's stay at the Grand!

Even for free it wasn't worth it. That place needs a refurb in the worst way. Our wifi didn't work the whole time we were there even after sending up 2 techs, there was 2 power outlets in the whole room, and the bathroom set up was like a fancified Motel 6. I mean, a sliding door for a bathroom door? It's one step up from a dorm room. And the room was TINY. Super small. The balcony was nice, but we were only out there with our morning coffee.
The whole time we were at the GCH we couldn't help but think we could be at Fancy Hotel X in any city in the world. It was nice enough, but it didn't say "Disney" to us, and when you have kids you want it to have that extra magic, ya know?
Don't get me wrong, being right next to DCA was very nice, and watching the monorail go by our balcony was very nice and exploring the architecture of the hotel was very nice but the Grand was a "one and done" for us. It's about a hundred more per night than the DLH and IMO definitely not worth it.