I have to be honest, I'm very much put off by the tone of the OP's post, as well as some of the replies. Someone wants to do something nice for a coworker. There are a lot of assumptions about the family situation - so what if DH always makes dinner, maybe his wife always does the shopping and since he has to do that, and make dinner plus the other things the wife normally contributes to the running of the household, it is a stressful time for them. Sure, they can do it, but some help would be appreciated.
My neighbor broke her leg a couple of weeks ago. I've brought her dinner a couple of times, we've helped with a few errands, etc. Yes, others in her family can and are doing a lot for her, but it is harder for them and we are trying to help. Another friend's mother just died after weeks of hospice care. Her husband is basically retired and she has 3 high school age children who are very nice and do a lot in general around the house. I volunteered to bring her dinner, but so many of us had volunteered by the time I'd tried to sign up, there were no dates left. She didn't need the dinners, but having people do this provided comfort.
This type of thing is about more than just meeting a need - it is about saying you care and want to help during a difficult time. Not wanting to do it is fine, but being put off that someone even asked for another person - well, as long as they aren't abusing the kindness being offered, I think this reaction is over-the-top and unnecessary. I hope there is more to this than the OP posted but based on what was posted, I fail to see why it was so wrong for the coworker to coordinate this for the woman with the broken foot.