@kathGIBSON,
If you want access to the kids you HAVE to maintain a good relationship with your daughter, even when you question the decisions she's making.
Be nice, hold your tongue, keep your opinions to yourself. Welcome your daughter, her boyfriend, and the kids into your home. That's the only way you'll be able to keep an eye on things. Feeling supported will help your daughter make better decisions.
Call CPS is you suspect abuse or neglect. Keep in mind that CPS's idea of abuse and neglect might be vastly different from your own. If your daughter thinks your being spiteful you can be assured of not seeing the kids for a long, long time.
You might have raised these kids but you also raised your daughter. Do you think you did a good job with her? If so, you have to trust her to raise her own kids. People most often repeat the way they were raised when parenting their own kids.