Hi GrandMotherof4 and welcome, if you are new!
The daughter of a friend has recently been diagnosed to and it has made such a difference to her life. I have gluten intolerance so am aware of how difficult it can be.
The supermarkets are full of stuff now that is GF and often approved by the coeliac society.
Nestles do a range of cereals. I eat the cornflakes and they are very nice. Schar bread, biscuits and crumpets are the best imo (though that is a comparative term) and the pasta that are out there are really good.
I reduce sauces and never add flour etc to thicken although cornflour is ok and I just substitute GF flour in cake recipes but make a larger quantity as they don't rise so much. And look out for recipes containing almonds and polenta.
Watch out for frozen chips and table sauces. HP tomato sauce has no gluten/wheat but most brown sauces and mustards do. Most of Sainsbury's sausages are now GF.
I'm sure you will all adapt before to long and your DGD and her family must be relieved to get a diagnosis.