Teams have to give rookie drivers a session in each of their cars once a season and Red Bull, who have already won both F1 championships, are leaving it until the end to fulfil their obligations.
"Jake Dennis is going to be driving one of the cars and Isack (Hadjar) will be in the other car," Horner told reporters.
Frenchman Hadjar also drove for Red Bull-owned AlphaTauri in first practice in Mexico.
Horner said Abu Dhabi was a circuit Red Bull already had plenty of data on and the first practice session had little set-up value since it was held in the heat of the day rather than at night.
Britain's Dennis, who won the all-electric Formula E title this year with Avalanche Andretti, has been carrying out a role as a Formula One simulator driver for Red Bull and is older than most rookies at 28.
Ferrari Academy driver Oliver Bearman, who drove for Haas in first practice on Friday, is 10 years younger.
