Cedeno's homer in the fourth inning put Houston ahead 4-1 and Laird's blast highlighted a five-run sixth as Astros took the rubber match of a three-game home series.
Laird also contributed a run-scoring double and both hitters finished 3-for-4 for Houston, which improved to 3-3 in its last six games.
Matt Dominguez had a pair of hits, including a two-run single, in the victory.
Lucas Harrell (2-2) held the Mariners on one run over seven innings, allowing six hits and a walk while striking out five.
Seattle starter Joe Saunders (1-3) was torched for eight runs on 11 hits over five innings.
Justin Smoak homered and Dustin Ackley went 3-for-4 with a run scored for the Mariners.