I wonder if your children would respond better to something like a WhatsApp group? Mine are much better at texting/messaging than they are at speaking on the phone, and I know that this is true of a lot of younger people.
We have a family WhatsApp group, and it gets used a lot. The beauty of it is that you (and perhaps more pertinently, they) can use it to respond immediately and 'chat', or they can pick up the messages when they aren't knee deep in children, cooking and all the other things that busy families have to do.
I will reiterate what others have said about you making contact, though. My own mum never calls her children, but expects everyone to call her. She often starts conversations with a complaint that nobody has been in touch, which is very unfair, as we do all speak to her often. I started to ask her how many times she had tried to catch us, and of course she hadn't.
She claims that she doesn't want to bother us when we are busy, but my sister and I have pointed out over and over again that if she calls, we (me, my sister, and her 6 grown-up grandchildren) will see the notification and will ring back, so there is no need to worry about being a nuisance.
She still won't make the effort, but now we just say 'well, the phone works both ways', or 'oh, sorry I must have missed your call', and change the subject. If that could apply to you, maybe think about calling your children, even now and again?
Since the lockdown, however, my sister and I have arranged times each day when we speak to our mum to break up her day a bit. Could you suggest that your children do the same? Or are you up for a video call, using something like FaceTime or Zoom?