Encouraging 5yo to sleep in his own bed.
He's probably going to feel displaced. The only other thing I can think of is that if there's something he would really like to do, you could explain "Mommy will have the energy to X if we can all get a good night's sleep." I would just make a consistent rule and enforce it. Gently lead him back to bed. Repeat. Repeat. Repeat. You deserve to get a decent night's sleep. Hang in there.
I've found that just being REALLY honest with my son has helped. I let him know that I was starting to feel really frustrated with the sleeping arrangements and we had to find a way for us both to sleep better so we could be happier and better rested during the day. One thing that helped me was putting my son in with my daughter (he's 5 and she's 7). He knows that he can come with either of us but that we are going to trust that it's an emergency / he REALLY needs to be in our space. It's not perfect, but it's working fairly well.