As usual, little information on the type of steel Honda use in the Advanced Compatibility Engineering™ (ACE™) Body Structure. I would safety assume that any of the colored stampings have some form of Ultra-high Strength Steel (UHSS) or Boron. Also take note of the side-impact door beams.
The ACE body structure incorporates a front-end frame structure that absorbs and disperses crash energy over a large area. ACE increases Odyssey passenger protection, and makes it more crash-compatible with vehicles of differing heights.
The Honda Odyssey has three rows of seating. So naturally any side impact airbag would cover all three rows. If the side impact air bags are not deployed. Use caution when making cuts to the B and C-pillars. There is most likely multiple inflators.
Just a little extra information. The Honda Odyssey earned a 5-star rating in frontal- and side-impact tests performed by the National Highway Traffic Safety Administration (NHTSA). That means there are some very tough parts of the body structure.