You could be having multiple problems and the solution for each is different.
First, you could be one of those new breed of managers who believes that everyone will do the best they can without much management. Unfortunatley, this type of managment philosphy doesn't prepare you to deal with people who are not interested in doing anything except what they want to do and who are poor performers. Your team resists even your mildest suggestions and you are treating them like that's OK. It isn't. It is not your job to be the friend of the people your manage, it is your job to get the work done. In this case, you may need to get tougher with people, there have to be consequences for ignoring reasonable requests.
You also state that you have some older workers who ignore what you have asked then to do. By chance were you promoted to this position when one or more of them expected to get it? If so, they may be punishing you and trying to make you look bad and you need to learn very quickly about office politics and how to handle disgruntled employees.
Or you could be dealing with a generational problem. Younger employees expect more freedom than older ones do. They especially resist doing anything that looks to them like administrative work like checking emails or writing them or attending meetings. You will need to explain to these types of people why these things are important and why they are causing problems. This can also be a problem with developers of all ages (who believe that anything that is not developing is worthless) although it is exacerbated in the young.
Or you could genuinely be expecting something that they find ridiculous and they are right.
Or you could be trying to change a long-standing cultural practice. And there is always resistance to change.
I think you need to sit down with people and feel them out for why your reasonable (well they seem reasonable to me) expectations seem so unreasonable to them.
Without more information it is hard to tell which of these types of issues (and there may be multiple causes) you are facing. What is your management style, what kind of workers are these and are they the types of workers you have supervised in the past. Id the overall quality of their work good and just these minor issues or are these the tip of the iceberg and the team is resisting you in lots of ways?