If i may i'd start with a couple of questions. Who told you he doesn't want to stay? Assuming you raised your DD according to your rules, have you had the conversation with her about this? Her answers may be hard to hear. Does she consider that you were 'too strict' and 'tough' with her and as a result is going the other way with her child. As long as he isn't behaving in a dangerous or destructive manner, what is he doing that is so bad?
Yes, good manners do matter (in my opinion) and as grandparents we are there to reinforce them. Yes, we have rules here when the GC come to stay, but not many. Each of our GC is different - one of them loved lego and building, our youngest, aged 6 is completely opposite - soldiers, guns is his current 'thing', as a result there is much clattering and banging when he is around. So in terms of 'doing what he wants' yes, to a point our GC do 'do what they want' when they are here. The more active one I take out on his bike, take him to the park in all weathers. The older one likes to play a game, so we wait until the little one is asleep and have quiet time with him.
We accept that our home will be chaotic whilst they are here. We have a bedroom for them where all their 'stuff' is kept, they both love rediscovering things they had forgotten about and i add/take away things as they grow - charity shops are brilliant to buy/donate things as their interests change.
Of course the ipads/tv's/phones are a point of contention at times, but wasn't it ever thus? I can remember being told i would get square eyes, or being moaned at that my head was in a book again when i should be doing homework, tidying my room etc. Even as an adult i can be found browsing the internet/watching something on TV instead of doing something more productive.
Talk to your daughter, bite your lip and hold your opinions to yourself unless asked and i hope you can build a relationship with your GS moving forward.
PS. Is it not a sweeping generalisation from some posters to say that parents these days do not seem to care about manners? Perhaps they would like to meet my DSIL's parents who are in their early 70's, my DSIL admitted he was dreading us meeting as he realised his parents, amongst other things, have awful table manners. Also, these days i work part time in a shop and i come across illmannered people of all ages.