I also recommend using getawaytoday.com. We booked our hotel through them for our March trip (and have used them for other trips in the past). We also bought 2 out of 4 parkhoppers through them. The other 2 parkhoppers we got free through Airmiles.
To give you an idea of the good deal with getawaytoday.com, we booked the Sheraton Garden Grove for 4 nights for $360 total, taxes included. The hotel-only package also included free dining for kiddies under 9yo, free daily parking, and free shuttle (Sheraton's own shuttle). We chose the Sheraton GG because being across the street from the parks is not a big deal for us; we like to drive to the parks, and our teen/tweenie kids don't need to return to the room to take naps.
With your young kids, you may want to choose a hotel that's walking distance to the parks. If you do, the HOJO has good entertainment book rates ($59-$89 depending on building/room location). However, those rates are limited to certain dates, which you can find out if you google "HOJO Entertainment rates"; the HOJO has a message board that posts the dates.
You mention you'll have a car, so good to pick a hotel with FREE parking, something that's becoming quite rare on S. Harbor hotels.
With park hopper tickets, check to see if
AAA sells tickets that include free parking at the Disney lots as parking is about $15/day at the Disney lots.