Off the top of my head, a second, larger strike against Rabaul would not be a bad move. Even if some of the ships and units that would have been at Rabaul have been sunk ITTL, I'm guessing the Japanese must still be planning to build up the base. A major strike by three carriers could be devastating.March 12, 1942 South of Diamond Head, Honolulu
Five carriers turned into the wind. Enterprise and Lexington were in Task Force 16 while the Atlantic Fleet reinforcements, Yorktown, Constellation and Hornet, formed Task Force 17. Destroyers waited for the course of the carriers to steady as they attempted to hold their screening positions during flight operations. Fifty three minutes later, the carriers slowed to normal cruising speed and the escorts tightened up on them. Over two hundred aircraft were launched, all heading north to “attack” a secondary army airfield on Oahu. Yorktown had finished launching her deck load strike first, every plane was up and assembling within twenty seven minutes while Hornet took the longest at forty seven minutes. The two Pacific Fleet carriers were only slightly faster than the rookie.
By nightfall, the exercise was done and the carriers headed back to Pearl. The Atlantic Fleet carriers had liberty tonight while Enterprise and Lexington would get liberty tomorrow night. The Shore Patrol had been overwhelmed with fist fights when the victors of the Norwegian Sea started having intense discussions with the pinprick raiders of the Pacific.
A strike against the Marshalls would also in my mind be a worthy goal. The only major warship that I know for sure is there would be the light cruiser Katori, but that area is still a key Japanese position. A strike there would also be good for ensuring the Japanese don't make any further moves against Wake Island.