One idea might be to present SoberLink as a sort of mutual peace-of-mind arrangement - if he's using SoberLink you know he's not drinking, and he knows you know he's not drinking, eliminating arguments about whether or not he's drinking. This is much more neutral and objective than having to rely on your own observations or third-hand reports from other people.
(He may not [probably won't] go for it, but if you make the offer in writing, that means that if you do go to court you can show that you offered a reasonable plan to ensure security of the kids and he refused).