I'm not a counselor, but I would suggest that even though it is gut-wrenching, you also need to look after your own psychological health, even though, at the same time, you care very much about your partner's psychological health.
In order to look after your own psychological health, I suggest you will need to find the courage to honestly face the possible reality that your partner might end up associating the grief with your relationship. Hopefully that won't happen, but it's better that you don't hide from that possibility, because if you hide from the possibility, it may hit you like a ton of bricks if it does become reality. I want to stress that this isn't about being pessimistic - it's just about steadying yourself about one possible outcome, so that you can at least be somewhat prepared for it, mentally.
I don't mean that your relationship was in any way to blame. I mean that sometimes when people go through a traumatic experience, they may associate it with something that was also present during the trauma, even though they logically understand that that something wasn't actually to blame for the traumatic experience.
As far as counseling and support groups, I can totally understand your partner's preference for face to face talking, but as a second best, perhaps video conferencing might be of some help? Undoubtedly, many other people are going through the same experience at the moment, and where there's a need for support, there's usually some way to provide it, even if it's just a support group set up by those who've had the same experience.
Also, remember to communicate with your children as openly as you reasonably can, rather than keeping everything behind closed doors. They will be going through trauma, too, and, just like you and your partner, they need not to feel isolated, too. You can't prevent them being traumatised by the situation, but making the effort to provide them with open communication could make an enormous difference to how well they handle the situation.