M.R.
When ours were little, the idea of time passing and how long it would be were really difficult too. We started a Daddy garden. I got a small american flag for each week that he would be gone, and we planted them under a tree. Each Sunday, one of the kids got to pull a flag out and put it into a vase on the mantel by his picture. As the vase got full and the flags were fewer and fewer in the garden, the kids could see how soon Daddy would be home. It was a nice way to share thoughts at a regular time, talked about how Daddy would like to play golf today, or how much he would like what we were having for lunch. When he could mangage to call on Sundays, that was helpful too.
Good luck, you will make it. We did not do any tapes, but that sounds like it would be a good idea. We have a lot of pictures around.
M.