My family unit are NC with BIL.
We ignore each other studiously; no communication of any sort is done between us. I have found the whole thing liberating, my DH has found it painful but has accepted it and realises that his brother will not change.
Ignore any gifts, cards, letters etc that are sent; any gifts can be taken to the charity shop and cards can be shredded. There must be no acknowledgement from you.
This is from Lightshouse:-
"Also, listening to phone messages, failing to block NC parties on Facebook, Twitter, etc., and accepting cards, letters, emails and gifts is not considered to be no contact. If you are called on the phone, the instant you realize who it is, the phone should be hung up without comment. If a message is being left (or about to be left) on an answering machine while you are present, simply pick up the call and immediately hang up to break contact. Call blocking is a tremendous help, and is inexpensive or free. Contact your phone service provider for details of available plans.
Mail is thrown out unopened. Returning mail to the sender is stimulating and rewarding to toxic people, and they are encouraged by it. They typically respond to returned mail by sending even more, so don't return it. Gifts should also be given away/thrown away unopened as well, unless harassment charges/court proceedings may come up and you feel you may want the items as potential future evidence that you were not left alone. (It is better to save them and not need them than need them and not have them.) If you wish to save them but would be too tempted or upset by their presence, immediately give them to a trusted third party.
Block your email. If anything gets through, as soon as you recognize the sender, it should be deleted without being opened or read. (Again, the exception to the rule would be if you felt you may need it as evidence of unwanted contact, in which case, you could save it without opening it, provided you did not feel a personal safety issue might be involved). In such cases, you may wish to have a trusted third party read the messages for you and let you know only if they contain any threats made against you. The rest of any messages would not be relayed to you.
If you need to keep the emails and the temptation to read them would be strong, arrange to forward all unopened emails to a third party who is not in any way connected to the person you are NC with. (A trustworthy friend of many years from work or a dependable neighbour friend are examples.) Choose this person very carefully; it should be someone completely unconnected to the NC party (total strangers to them are best) and someone who is trusted and capable of holding the emails without losing them or otherwise putting them at risk carelessly.
Emails, letters, and phone calls from third parties should be treated similarly. The caller or sender should immediately be told that you will not discuss the matter with anyone, and that they are not to call about, write about, or raise the issue with you ever again.
The most common mistake made by people who are initiating no contact is allowing third party communication to leak through to them. Stop people immediately if they begin telling you anything, and let them know you'll no longer hear anything about people with whom you are NC. If the person refuses to respect your wishes, you may opt to limit contact with them as well.
Many people who have gone no contact from a toxic, destructive relationship feel it is the best thing they have ever done, and the first time they have felt freedom from manipulation, drama and other forms of emotional abuse".
I would reiterate what Hissy has written; grandparents have no automatic right of access in this country re their grandchildren.