Ocean isle might be a long drive depending on what part of Myrtle Beach you are staying in. If you are in North Myrtle it might be ok, but if you are in MB or farther south (Surfside Beach, garden City, ect) then you will probably want to consider a charter out of Murrels Inlet. Captain Dicks Marina has Gulfstream charter boats as well as head boats. There is also Marlin Quay Marina and Voyagers View which also have several charter boats as well.
Captain dicks marina www.captdicks.com
Voyagers View ph #843-651-7033
Marlin Quay www.marlinquay.com
April is a great time to catch tuna, the georgetown hole is always hot. When you look at the charter prices remember that it is a long run from MI to the break(30 fathom line) 56 nm and 70 nm to the georgetown hole. The boats farther north (ocean isle) spend a lot of time fishing the blackjack hole which is about 65 nm from MI(probably about the same run from OI, but I am not sure.