Yes, this is the right place ameron. I'm so sorry that having been such a huge part of your GC's lives you have been stopped from seeing them. They are going to miss you just as much as you'll miss them.
It's difficult to know what to say with such little information. Do you know their new address? If so, you could send the children cards for their birthdays and at Christmas.
We did this for 7 years only stopping last year and bought 2, one to be posted and one for their memory box. If you don't have an address or decide to not to post cards, getting them one every year will show one day that even though you were stopped from seeing them, you continued to love them.
There are several estranged parents and grand parents who regularly post on this forum myself included, who will be here for you if you want to talk.