Are there any grandparents raising their grandkids because their parents couldnt?

My husband and I have just be awarded full custody of our granddaughter who is 6mnths old we have already raised 7 kids and our youngest is only 12 yrs old..how do others in my situation cope...is it ok that she calls us mom and dad (although we will always teach her who her mommy is)..is it ok that we out limitations on the access..our daughter has bipolar disorder which means she gets very volitile and aggressive very quickly and so we currently allow her to come and stay every 2 weeks for 4 days to spend time with the baby..isince our granddaughter was born we have been responsible for her financially now that its through the court system and we have her until we die is it wrong of us to seek child support would love to hear from others in my situation