First I want to say that I am very sorry you have this pain to carry. similary our anniversary followed a similar time frame after D-day.
I felt divided about how to approach it.
I am guessing there is no way to avoid you husband being away at that time?
His being away could provide a reasonable rationale for why you are postponing your marking of the day to family members and children. and on his return what is in fact a low key meal out for the two of you could just be offered to others as 'your occasion'
However, I can understand your concerns that regardless of the above challenge the deeper concern is what the milestone itself brings up.
His you H being supportive and remorseful? If so can you arrange some Skype time and telephone time on the actual day and the evening before and after?
Or journaling either at home or through SI during the time and exploring those feelings and thoughts.
For me I took the day off work and had the children with me. I either spent time with them or I spent time writing. We also took a couple of hours out and used it to talk and explore my feelings.
Others just assumed we were having some romantic time. We let them assume that - and it allowed us some time to ourselves.
You could plan something like that for his return - along the lines of what you would usually do a meal out or an evening away. But between yourselves understand that it will time to work through another layer of what is happening for you.
I agree - I was no where near ready to celebrate.
In my case I was ready to reclaim a few things, and because I felt committed to the marriage and also concerned for my children I tried to find a balance and saw an opportunity to reassure my children as they had been aware of a lot of the tension and pain between us.
best wishes to you PBM -