I'd probably send them a postcard first if you have a few weeks. Then when you call, you can say, "I'm Account Closed who sent you a postcard. I know you may have received, but I am a fair, equitable, local guy calling to see if you need help in any way. Would you like to go over some options?" Something like that.
There are benefits to cold calling too, if you can find their number. Speed may be more important facing a deadline like this. Maybe even say you were going to mail something, but with the time crunch, thought it best to call directly. Good luck!
One option is to not know they're in foreclosure. You're a real estate investor looking to buy a house like theirs in that neighborhood, and you want to know if they have intentions or thoughts about selling their property.
The less recommended way is to mention you know about their situation - but you don't want to embarrass anyone. Ask what they intend to do; list it, sell it, refinance it, get a second etc. and see where can you bring value to them. Some people elude themselves to think they can solve it whereas the mortgage lates have already been written on their credit profile. That's where you can come in, but it's vital to follow up and not wait for a call.