Song suggestion for breast cancer benefit?

I am doing a Male "Beauty Pageant" with a talent portion. I'm an accomplished musician and singer. I plan on playing acoustic guitar and singing. My girlfriend's sister has breast cancer and is the main reason I'm doing it. They are very close as sisters and I'd like the song to be about strength and love. But I'm also considering on using this event to propose to my girlfriend. I've attempted writing the song but I'm hitting a little block. So if you can think of an uplifting song, or a good love song that would go over well at an event like this I'd appreciate input and suggestions. Or lyrical suggestions could help too.thank you in advance. please no trolling, this event means a lot to me. Besides the obvious songs like Im gonna love you through it. Im sure this song will be played during a few segments of the night