I think there are lots of different types of arrangement possible, without short changing yourselves.
If DH loves you, you are short changing him by faking being in a real marriage. You are short changing him by stopping him finding someone that does love him.
You are short changing yourself for settling for this. It sounds more like an arranged marriage - they work in some cultures as love is considered a bonus in a marriage, not an essential, and it's about a working partnership and family. But that's not our culture. We normally do expect love as well. And it seems very sad to turn away from that.
But you wouldn't be the only couple to do this.
However ...what then happens when your children are grown up and your reason for staying together is gone. If it seems scary to start a new type of life now, think how scary it will be in 18 years time.
I think you need to consider other possibilities. Not all divorces end up in disaster and agony. You only hear about those ones. Many are amicable arrangements.
Me and my ex husband split up and kept things very amicable. While he did move away and it was tough to be a single parent, it was better for me overall. Also, he was still a very involved parent, loads of contact, holiday time at Dad's house, attending all school and hobby events etc. although I wouldn't go so far as to say co-parenting. My son did eventually go and live with him for a year to attend a specific college. It doesn't have to be doom and gloom.
For more of a co-parenting thing, I have two examples for you:
Two friends were in a relationship, had a baby, but it wasn't working between them. They split up when child was around 4 years old. He was very calm and non-stressed about it (honestly!) because they co-parented. They really did share the care with him spending pretty much equal time with both. In fact they still get on so well as friends that 25 years later they still go on holiday together - she now has a toddler with her current partner and the original man is very involved there as well! Like a 2nd Dad. It all seems to work out very nicely.
I met a couple who'd split up, divorced, but stayed in the same house by turning it into two apartments. One larger one with her and the kids, and a smaller one for him. That way they both coparented and children moved freely between the two apartments, considering them both home.