Yes, I am not clear what the problem is. Is it minor - like no sweets, or vegetarian only, or is it something major, like - well I cannot think of anything off hand.
You clearly still see the children and have them to yourselves. Looking back on three generations of being grandchildren, me, my children and now grandchildren, relationships with grandparents have been based on who the grandparents were rather than what they did for us, gave us etc. Mak it clear when refusals are based on Parents Rules, we all have them/had them.
I would suggests top constantly comparing yourself with the other grandparents, worrying about what your children's motives are and just enjoy your grandchildren in the here and now when they are with you and let the rest go hang.