I didn't personally co-sleep with my kids except for allowing several minutes they could lie next to me and calm down when they had a nightmare, but I try not to judge. Whenever you think it's time (assuming they are able to walk/crawl out of bed, of course), a method I've heard called "sleep separation" works pretty well as a compromise between "sleeping in their bed or in their room next to them" and "walking away and closing the door to let them cry it out" methods.
Especially if they are still at an age where they sleep longer than you, you sit in their room, awake, but refuse to interact with them (facing away is helpful and recommended), until they are asleep. You gradually increasing the distance from them over the course of several days to MAYBE two weeks, until you are out of their room and the door is eventually closed.
If/when they get up, you react in the following ways:
- first time, you correct them with a decent number of words ("I know you want to be with me, but it's time to go to sleep. Goodnight. I'll see you in the morning") and maybe a hug/kiss/tucking them in, etc. Then resume your sitting place
- second time, you correct them with as few words as possible ("It's bedtime"), maybe helping them cover up with a blanket. Then resume your sitting place
- third time and after, no words, no helping them with their blanket, but gently guide/carry them to their bed and resume your sitting position. Again, without words.
This method has the benefits of them knowing where you are and knowing that you are not abandoning them, but does not play into the game of "I don't want to sleep". You are awake and able to react quickly and in a controlled manner, and you start gently and lovingly, but quickly just get to the point of helping them to be where they need to be.
If they have fallen asleep and you have left the room, but they wake to find you gone and they come searching, it is essentially a rinse and repeat, except you go back to your room or couch or wherever you are when not in their room.
- first time, explain the situation with a reasonable number of words ("no, you're sleeping in your own room now. I love you. Goodnight"), tuck them in again, etc.
- second time, as few words as possible, guide/carry them as necessary to their bed (a single "Goodnight")
- third time and after, no words, guide/carry them as necessary to their bed and walk away, closing the door
If you're going to increase the number of steps before you use no words, I highly recommend increasing to no more than four gradations as compared to the three I outlined above. They are human beings and they are intelligent. They understand what they are doing and they can understand what is expected of them. Further explanations can happen before bedtime (if you want to introduce them to the idea of sleeping in their own bed with a discussion), or the following morning. Bed time is not the time for philosophical discussions or nuance.