<font color=navy>I think any Disney hotel will be fun to stay at - I've stayed at the DL Hotel a couple of times and the Grand Californian a couple of times.
The Grand Californian has a richer, darker wood theme. The rooms have a nice balcony with a couple of chairs and a table out there. The lobby is huge and welcoming, with a big fireplace. If granny needs a quiet place to relax while the youngsters run around the parks, then the Grand Californian is a good choice - you can use the lobby lounge whether or not you're staying there. If you have small kids who'll take advantage of the many water areas at California Adventure, then you might want to consider staying at the Grand Californian where you can just pop up to the room for a quick change of clothes, or a nap, if need be.
The DL Hotel has a lighter theme, white-washed furniture, with a sprinkling of Disney throughout the rooms. There is no balcony, however, there are sliding glass doors, and a ledge you can step onto for a breath of fresh air. There are waterfalls, a pool with a 'beach' and the Neverland Themed pool, which is popular with kids. There is a koi pond & you can help feed the koi a couple of times a day. If you stay at the Bonita Tower, you can do the same as if you stay at Paradise Pier when going to Disneyland and cut through the Grand Californian to save time.
Anyone staying at the hotels gets front of the line monorail passes.