Speaking from personal experience, I would send flowers and a 'thinking of you' card signed by both of you and on behalf of your children. If she responds you can take it from there. If not, at least your conscience will be clear and you'll have done the right thing morally. I'd encourage your dh to contact her too. If she rebuffs your efforts at least you'll know that you've tried.
In my case, my SIL was extremely jealous of the closeness my dh and I share. She tried to break us up, using lies, several times and we ended up not speaking for about the last 3-4 years out of the 11 yrs we were together (although she would call when she was drunk just to talk about once a month; but not for the last 2 yrs).
The relationship soured after the first year when we moved away and although it was DH's choice to do so, I got the blame and things went downhill from there.
They'd had a close relationship and I think she blamed me for coming between them, even though they still spoke 3x weekly. My DH insisted we go NC after the last break up attempt, and although I wanted him to stay in contact, he wouldn't as he was so angry with her and fed up of her histrionics.
We didn't realise how bad things had become for her until we received a late night phonecall saying she'd committed suicide, aged 39. The last 2yrs had been really difficult as it had driven a wedge between us and her and DH's parents so we hadn't really spoken to them either.
We went to the funeral and it was the start of healing the rift between PIL and us. We realised how fragile life is and I wish we'd tried harder to at least stay in touch on our side with her (Christmas/birthday cards, etc). I regret what happened and feel sorry that my DH's last memories of her aren't great ones, and I know he wishes he'd done more. The only good thing is that it's brought the rest of us closer together.