Hi Squidge,
If they are too difficult/toxic/awful for you to deal with they are far too toxic for your both vulnerable and defenceless children. They saw through them years ago as well, they saw their dislike of you as their mother as well as their disinterest and have acted accordingly. Apart from anything else, young people need positive role models and your parents are anything but those. Would not have even offered them therefore even one night with them. Your parents are used to riding rough shod over any boundary you care to set as well.
You being the reasonable person you are write that you do not want to hurt them but they have never thought twice about hurting you emotionally have they?. They truly do not deserve any consideration from you. You owe them nothing and they will also never apologise nor accept any responsibility for their actions.
As you rightly say you cannot force your children to go to their GPs and they do not want to go to see them anyway.
Many people, when first attempting to go no contact, make minor errors that lead to stressful consequences. Here's how to avoid them...
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Ideally, a toxic person with whom you are refusing contact should be told (in some way) that you are no longer willing to have contact with them, or else they can't be expected to stop calling, writing or visiting. Many people write a simple no contact letter stating that they consider the relationship over and do not wish to be contacted in any way again. However, some people feel the person already knows (or should know) that they clearly don't want a relationship and they opt not to send a letter. There are certain drawbacks to the option -- you may worry the process is more likely to be interrupted if you haven't clearly announced your intentions.
Some who opt not to write a NC letter do so because they believe sending a letter is engaging the person more, which they don't want. If the party they are seeking NC with continues to seek contact, they typically put it down in writing at that point. However, you will be the best judge of what is right for your situation.
No contact means no contact. If you are going NC but plan on keeping touch with mutual friends or family, you will need to make it clear at some point that you do not want to discuss anything about people with whom you have gone NC. Do not accept information and triangulation with third parties. Interrupt them immediately and tell them not to continue.
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 neighbor 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 also suggest you read "Toxic Parents" written by Susan Forward as a starting point as well as writing on the "well we took you to Stately Homes" thread on these pages. You will also get support there.