Ighalo will be unavailable due to club committments.
Okoro is currently involved with the Super Eagles B side in the Wafu Cup.
The game has also been moved by a day, from May 30 to May 29, to allow the squad enough preparation time for their June 5 Olympic qualifier against Tanzania in Dar es Salaam.
Team spokesman Arafat Aliu says the squad are expected to depart the country on the May 26 and return on May 31 before departing for Tanzania on June 2 for the first leg second round Olympic game qualifier.
Other players to make the trip to the Central America country include: Nosa Igiebor, Edet Ibok, Orelesi Nurudeen, Emmanuel Anyanwu, Terna Suswan, Obiora Nwankwo, Ekigho Ehiosun, Saka Ayo, Udoh Kingsley, Solomon Okpako, Oduamadi Nnamdi, Harmony Ikande, Oseni Ganiyu, Uchechi Daniel, Sone Aluko, Thomas Femi and Ajiboye Muniru.
Nigeria Football Federation Technical committee member Austel Elumelu will lead the delegation to Costa Rica.