I apparently am in the minority... but, I don't think it is too much to ask. I know that some kids, usually boys, are high energy and don't like to sit still. I know it can be a lot of work for the parents. I know that you don't think he will "get anything out of it". BUT, no matter how old he is, he isn't going to magically start sitting still for an hour for church. It is a skill, like anything else you want him to learn, and he will have to be taught. Our son was getting the hang of it before the age of 3. It took a year or so before he really was able to tolerate the length of the service and be still and quiet. BUT it wasn't horrible while he was learning. And he did learn. When we changed churches he was 6 and our daughter was 3. The entire congregation seemed amazed that both our kids were so well behaved during the service. My husband wasn't even present 99% of the time due to his work schedule at the time, but little ol' mommy was able to manage them both with no problems. My daughter, who started learning to read shortly after that, by age 4 was following along in the hymnal singing the hymns and speaking the responses during the liturgy.
It is a must to talk to your son in advance. Not just once... but the day before (Saturday), in the car on the way to church on Sunday, and before the service starts... explain to him what you expect him to do. When everyone stands, he should stand and face the front like everyone else. When everyone bows for prayer, he should too. If there is a kneeler, it is not a toy or footrest... Tell him what to do if he has a question. Or if he needs to use the potty. And what is NOT allowed.. (kicking the seat in front, standing in the pew, talking, banging toys, making noise with paper or crayons, etc).
Have him think of it as a grown up thing. It's a reward for him. It's important for you as a family that he be part of it. Then AFTER the service, praise him for what he did well... or what he DIDN'T do that you saw another kid doing. Ask him some questions about the service. Explain some aspects of the service... (the pastor will___. That is when we ___. Did you see the ____ ? We use that for ____).
You might even consider taking him every other Sunday at first.
And keep in mind... our little ones absorb far more than we give them credit for. He may not listen to the sermon like an adult or an older child.. but he will observe the reverence of the other congregants, the pastor, and YOU. And he will learn the reverence given the altar and what goes on. He WILL hear some things..though he may not understand... and eventually he will start asking you questions about what he hears... which is a GREAT place to be!
I suggest you bring one or two small handheld toys (a bendable Spiderman figure or something quiet that he can manipulate), and only let him hold one at a time. Take turns with your hubby... he gets the first 10 minutes, then you get the next 10, etc. Have your son sit to one side of whichever of you is in "charge" so that there is another congregant to the other side. If your son is the LEAST bit shy of "strangers", he will sit really close to you and very still to avoid touching or being close to the "stranger"... and that helps him be still, plus he will be entertained looking (checking out, lol) the person's clothes or shoes or just staring... whatever. So don't sit beside your best friend, lol. And try NOT to sit on an empty pew. I have observed watching other small kids.. that wide open spaces like that tend to tempt the kids to slide all around on them, lay on them wallowing around banging feet, and generally testing their boundaries in a way they won't if there is someone occupying the space.
Good luck. It is worth it in the end.