I'm not sure if you're playing on or offline against the IC's. But if you're playing online, then doing what you're doing can be a little more difficult. The number one thing you want to do is separate both Popo and Nana. And the best way to do that is to nair them. The question is, do they block whenever you attempt that? Because if they do, then it's going to be kind of hard to successfully split them apart as they have the advantage by just shield grabbing. Of course this all sounds harder than it actually is.
If they're spacing with their Flurry (Down + B), you could try and get above them with nair or maybe space yourself and use PK Thunder. You may even be able to get an aerial PK Fire in there since when they attack, they'll be left open. PK Fire can be troublesome for these two, I believe. And it's because there are two of them who have to deal with it and both don't share the same damage. Keep in mind that these two don't exactly have the best grab game in this game, which is ironic. But once they do get you, then you're pretty much screwed.
Anyway, I think a little grounded PK Fire may also help if they're coming at you with their Flurry or trying to close in with their Ice Shots. Basically all you've really got to do is separate the two and you should be fine. When they're separated, things kind of get a little sloppy for them. If they're not coming at you with their Flurry, then they should be a little easier to deal with if you ask me.
If they're spacing with their Flurry (Down + B), you could try and get above them with nair or maybe space yourself and use PK Thunder. You may even be able to get an aerial PK Fire in there since when they attack, they'll be left open. PK Fire can be troublesome for these two, I believe. And it's because there are two of them who have to deal with it and both don't share the same damage. Keep in mind that these two don't exactly have the best grab game in this game, which is ironic. But once they do get you, then you're pretty much screwed.
Anyway, I think a little grounded PK Fire may also help if they're coming at you with their Flurry or trying to close in with their Ice Shots. Basically all you've really got to do is separate the two and you should be fine. When they're separated, things kind of get a little sloppy for them. If they're not coming at you with their Flurry, then they should be a little easier to deal with if you ask me.