I looked up the IJN carrier movements on the combined fleet website
http://www.combinedfleet.com/cvlist.htm
Here is where they were for March and April 1942.
Kaga
5-Mar Operations off of Java.
15-Mar Return to Japan to repair hull damage incurred at Palau (non combat)
22-Mar Arrives Japan
4-May Repairs completed
Akagi
9-Mar In fleet anchorage in Borneo
26-Mar Indian Ocean operation
19-Apr Departs Japan with Soryu and Hiryu in pursuit of Hornet and Enterprise. The TROM is not clear when the Akagi left the Indian Ocean
22-Apr back in Japan
Soryu
1-Mar Operations off of Java.
11-Mar In fleet anchorage in Borneo
26-Mar Indian Ocean operation
18-Apr Departs Japan with Akagi and Hiryu in pursuit of Hornet and Enterprise. The TROM is not clear when the Soryu left the Indian Ocean
22-Apr Back in Japan
Hiryu
1-Mar Operations off of Java.
11-Mar In fleet anchorage in Borneo
26-Mar Indian Ocean operation
18-Apr Departs Japan with Akagi and Soryu in pursuit of Hornet and Enterprise. The TROM is not clear when the Hiryu left the Indian Ocean
22-Apr Back in Japan
Shokaku
16-Mar Left Japan
24-Mar In fleet anchorage in Borneo
26-Mar Indian Ocean operation
18-Apr Back in Japan. The TROM is not clear when Shokaku left the Indian Ocean.
19-Apr Leave Japan with Zuikaku for Truk
Zuikaku
16-Mar Left Japan
24-Mar In fleet anchorage in Borneo
26-Mar Indian Ocean operation
18-Apr Back in Japan. The TROM is not clear for when the Zuikaku left the Indian Ocean
19-Apr Leave Japan with Shokaku for Truk
Since Ceylon was raided on April 9th, they had to have been out of the Indian Ocean soon after that so as to be back to Japan by April 18th.
I dont see where the operation of the carriers would have relieved pressure off of the USN as by the time the allies knew the carriers were in that ocean, there was no time to really do anything about it to take advantage of the situation. Plus once they cleared the seaway off of Singapore, the carriers were only a couple of days to cruise to get to Pulau or Truk.