Ganon doesn't really want to be attacking IC's shield as often as other chars imo. That dsmash punishes nicely, and L-canceling can be trickier since IC's have 2 shields. Properly-spaced ftilts, bairs, and retreating fairs usually work well. Ideally I'd try to be patient and wait for an opening to approach safely, and seize any opportunity to separate the climbers/safely kill Nana.
If Ganon isn't attacking, then ICs will be moving in with grabs/Dsmash/shield and react. Spacing allows the ICs to get in closer after the attack, and if you jab and they shield again then you're almost out of room to space with.
What do you do to be patient with Ganon? Wait for them to attack by....?
Samus doesn't seem like she can get in well enough to Dsmash the ICs. Falcon has the running speed, the fall speed, and the knockback required for the knee to separate the climbers well. Falcon can also combo into the knee on just one or both of the ICs better (Dthrow, Dair, and knee are the first three moves that come to mind), which can lead to early deaths for one or both of the ICs if he gets a hit in at any percent.
Samus' Dsmash, while still effective, will not begin to work really well until probably mid percents. Also, ICs will be expecting the Dsmash since Samus doesn't have several other moves with the priority to beat ICs quick smashes.