How to find the best options for reward ticket?

Hi all-

I'm a little overwhelmed trying to find a reward ticket. I know that I am doing this on short notice and not under the best circumstances, but it's with good reason. I'm hoping for some advice as I try to find my way to the best option.

We have a very dear friend who's been diagnosed with Lou Gehrig's. He, his wife and son are renting a house in Cornwall, England in July and would like us to be there for part of the time if possible. It is likely the last time our friend will be able to travel and enjoy it. My husband has 500,000+ miles on AA - and although I'm not going to be using these miles optimally, I feel like it's times like these that I should rely on the miles to get us where we need to be. I know fees flying into/out of LHR are terrible, but I'm not sure we can avoid them.

Basically, this is what I'm trying to find:

Flights to UK (LHR or elsewhere) from ORD from about July 11-20. Our dates can be a little flexible if it would make any difference. Any advice as to how to best go about this so as to use the miles as necessary but not foolishly?

Thanks for any help or advice you might have. Off to start looking...