Where will you be driving from -- north or south of DLR? If you will be driving from north of the parks, it will be easier to park in the Mickey & Friends parking structure (on
Disneyland Dr., just south of Ball Rd.). This is a very large, multilevel parking structure. There is regular, handicap, and preferred parking (the non-handicap spots closest to the escalators/elevators). Parking is $25/day with in and out privileges. Preferred is $45/day (I think). M&F has its own bag check/security check point. Guests must go through bag check before boarding the free trams to DTD -- the drop off/loading area is a short walk to the ticket booths and the park gates (maybe 3-5 minutes).
If you will be driving from south of the parks, it will be easier to park at the Toy Story lot (on Harbor Blvd., south of Katella). Again, parking is $25/day with in and out privileges. There are free shuttle buses to the parks. You will go through bag check/security once you exit the buses at the Harbor entrance to the parks.
If you look on Google maps, all this will be easier to follow.
Is this a one day visit? For the least amount of walking to the parks, if there aren't any budget restrictions, I would probably go with M&F and pay for preferred parking to guarantee a spot close to the escalators/elevator. I don't know if TS has preferred parking by the shuttle stops.