Do not send them. Regardless of whether the charges are fully accurate or the situation is more complicated than the paperwork suggests, sending photos of children to someone housed on a charge involving minors is not going to end well for anyone involved.
Here is the practical reality. Mailroom staff at every facility review incoming photos, and an inmate flagged for a child-related offense will have their mail scrutinized more carefully than most. Photos of children sent to that inmate will almost certainly be confiscated before they ever reach him. Beyond not arriving, the attempt itself can draw negative attention to his record at exactly the time when keeping a clean profile matters most.
There is also a common-sense dimension here that is worth stating plainly. Whatever the truth of the charges, the optics of photos of children going to someone accused of an offense involving minors are impossible to defend, and the facility is not going to pause to hear the backstory before making a decision about what comes through their mailroom.
If the goal is to maintain a connection with family or friends who happen to be children, there are other ways to do that. Letters, drawings, cards, descriptions of what the kids are up to, all of those communicate the same warmth without creating a problem. Photos of adults are fine. Photos of children in this specific situation are not worth the risk to him or to you.