Thinking about this for next year!
We put a lot of effort into Christmas this year for 4, nearly 5 years old DS who was really into it for the first time.writing and posting letters to the north pole, grotto visit, wrapping the requested present in separate wrapping paper and getting a label printed so it looked different to his other ones, getting a magic key, watching Santa tracker etc. Maybe it's just the standard stuff but it was nice seeing him begin to 'believe'.
We also said father Christmas only brings one present as there isn't space for multiple ones for everyone.
On Christmas Day he was delighted. Then we went to grandparents on boxing day and they said Santa forgot all your presents here and directed him to a pile of presents! The labels said love from Grandma and grandad 😬 they were also nothing to do with the hot wheels/ monster truck stuff he had requested. He looked very confused and a bit taken aback, and didn't really react to the presents when opening them. Eventually he just cracked on with the day and playing with family and new toys etc. I asked him to thank his grandparents for all the presents they had bought and I think he got the idea that they were pretending about santa having forgot them.
I didn't want to be a misery at the time as grandparents probably didn't think it through, but would I be unreasonable to ask that next year grandparents just say the presents are from them and say Santa just comes to our house? I just think there's precious few years where kids really believe and I don't want him questioning it so soon!
I also personally prefer that he ask for and receive one present from both a sustainability point of view, and that he doesn't get loads whilst some friends get very little, but that don't really my main reasoning.