My two biggest tips are to go early (use early entry if you have it or be ready to line up for regular park open if you don’t) and be flexible.
Going early will mean you definitely want to take a nap/midday break, but you do run the risk of NOT being able to re-enter Disneyland due to capacity closures. DCA has never (in my knowledge) had a capacity closure so if you are ok with your evening plans being flexible and/or exclusively in DCA then definitely take the break. If you are dead-set on being in DL for any specific reason, then stay in the parks & use a combination of high capacity attractions, a sit-down meal and shows to take a break within the parks. If it were me, I’d hit Disneyland all morning, take the break at 1pm, come back to DCA at 5pm & then head to DL sometime between 8-10pm to close out that side.