<font color=navy>We go to DLR a lot, sometimes just to hang out at Downtown Disney. I often see guests in their suits & towels either headed to or coming back from the Disneyland Hotel pool, so I would feel safe to guess that you can pool hop between the three pools.
I was at the Paradise Pier hotel not too long ago, and you take the elevator to the third floor to access the roof-top pool. It's nice, but not themed - however, if you want a quiet place, you might consider it -- it faces the west, away from the parks, so your view would be the parking lot and the Disneyland Hotel (if you were to go to the perimeter wall to look out).
I've stayed at both the Disneyland and Grand Californian, and it's hard for me to say which hotel I prefer. I like them both very much for different reasons.
The Grand Californian has a more luxurious feel to it, and has an ambience of a lodge with its use of dark wood, lobby with high ceiling, etc. One of the things that I prefer in this hotel is that there is a lobby that welcomes you to relax and take a breather. There is a pianist in the afternoons, a huge fireplace, and a lounge right there, too. The Disneyland hotel doesn't really offer that. Yes, there is a small area to sit in the three towers, but no real place to congregate and just visit. I love to people watch in the lobby of the Grand Californian. And, when I was in a city view standard room (4101), I could leave my door ajar & listen to the piano, or go to the third floor where there is a little sitting area, and go there. It was nice. The Grand Californian also has a nice balcony where you can go outside and sit at a table & relax. (I've stayed in a room with a city view that looks out towards DL & PP hotels, and I've stayed in a room with a view of Downtown Disney). The pool has already been described, and I would recommend it for a fun pool (with slide), and without the big crowds.
The Disneyland Hotel has rooms with a lighter look to them - kind of like staying in a room on Main Street - at least, that's the feel I get when I go. The wood is lighter, and the decor is a little more whimsical. I also like the set-up of the rooms. We stayed in the Bonita Tower (I've also stayed at the Marina before the rooms were refurbished, back in '95), and were over the waterfalls, looking out through the pine trees - which I really liked. The sliding door opens and there is a tiny landing with a railing that allows you to barely step out of your room and get fresh air, or just watch. The desk was set apart, and separated with a little wall, so I was able to use my laptop & have the light on without disturbing my children. Also, the room came with a fridge that we could use. The Grand Californian has a stocked fridge with a tiny area for a couple of bottles of water, soda, or baby bottle. If you touch anything, you'll be charged because it has a sensor on it. The Disneyland Hotel gave us the fridge that we could use. The DL Hotel also had the Neverland pool, which was described (and is usually pretty crowded), and another, more secluded pool, with a wading pool next to it, and a sandy area with a volleyball court. It's nice.
In answer to your other question, park tickets come separately. I recommend checking the prices for a package, which includes room & tickets, or getting the room & tickets separately. Sometimes it's less to get a package. There are various agencies, and if you click on the link in my signature, you'll reach Dreams Unlimited, which is affiliated with these boards.
Character Breakfasts 
are fun to do. There are 4 in all. The best by far is Goofy's Kitchen located inside the Disneyland Hotel. In my opinion the worst was at Disney's Grand Californian, very boring barely any characters and they do not table hop for photos. The other two are Minnie & Friends located at Paradise Pier and Winnie the Pooh characters at the Plaza Inn located inside Disneyland at the end of main street on the right. All but Plaza Inn take reservations and if you do Goofy's Kitchen I strongly recommend you do this, otherwise the wait could be 15 min or 45 min.
