I don't have any personal experience with this, but agree that there would be a huge amount of risk, and potentially harm could be caused that can't be undone, and that would be so incredibly sad for a very happy relationship to end.
Please correct me of course if I'm wrong, but it sounds like that this open marriage would mainly be with the focus on sex with other people rather than wanting to have multiple "full time" relationships?
I think it's a really easy thing to say that you or your husband aren't the type to get jealous, but if you've been in a monogamous relationship, then what's your reference point for that in this particular context?
There are so many things to consider. What if one of you develops feelings for another person? How will that impact your relationship with each other? Even though you're not jealous, will you feel like you're being unfaithful (even though consensual) if you're sleeping with someone else and think of your husband at home? What if the person you/him are sleeping with develops feelings for you or him? How would that work within your family dynamic? What if one of you has lots of dates and one of you doesn't? Will the other person feel resentful or feel like they're not good enough?
I think you need to figure out if this is just a fantasy or a reality for your relationship, and my personal opinion would be that if that either of you have any doubts whatsoever it's not worth risking what you have to find out.
Sorry, I really don't mean to sound callous and it's honestly not how it's meant to come across, but just some of the things I would be cosidering with a decision like this. Whatever you decide, hope it works out x