I was going to say that no response is the best (destroy the cheque and no note). But, on further reflection, I think your husband needs to think long and hard about what he wants from his father and their relationship.
The urge to send an angry note back does not sound like someone who is ready to really cut off his father. He still wants to engage him and have a relationship (yes, angry notes are relationships).
So he should think
1) If he wants a relationship, he should look at family counseling (use the cheque to fund such mediation).
2) If he wants a low drama continuing pseudo-relationship, go with the Teflon approach (write a terse thank-you note and bank the cheque for something dull-future childrenís education, health insurance payments, retirement fund)
3) If he wants continuing relationship of drama and anger, write a nasty-gram.
Neither of you seem willing or able to truly detach. I donít think thatís bad. This is all fresh and very wounding. Itís just that I donít think that either of you should be making permanent relationship decisions.
Strong emotions are like being drunk. No irrevocable decisions should be made at this time.
(Personally, I am liking the idea of using the money for relationship counseling for your husband and you. Healthy communication ideas for your family and such)