If I were you, allow the fry to survive in the community. Locate your angels in the large tank as soon as possible to avoid stunting their growth.
Platies and other livebearers are very prolific anyway. A single mating from a male results to several batches of fry.
Try one female which has been around with males for awhile. Put her in a tank alone and you'll be surprised why she keeps producing without a male.
Their being prolific makes me hated them as they can strain your filter bioload due to added fry which also results to added fish wastes. I never bought livebearers since I came back from the hobby last February.
I knew this fish will give me troubles as the fry can be agile and good at hiding.
I've had it with them. It started with about 20 guppies which then made it to almost 200 in my tank months later.
The same will happened to your platies.
Well, it's up to you whether you'd raise them or not. Good luck.
On the food, the livebearer fry will eat anything.