N.B.
I had a daycare family with Colonel Daddy deployed for a year. Little boy was almost 2 years old till almost 3 years old.
Mom got him 2 Daddy dolls (one for home and one for daycare). They were GREAT! Here at my house, he talked to the doll (like it WAS daddy), sang him songs, read him books, slept with him, etc. I encouraged this heavily. Colonel Daddy Doll (thats what the rest of the kids called it) did story time with us, sat at the pic nic table while we played outdoors, etc. Some days he was more present in the play and in little boys arms, other days he stayed on the shelf nearby, but always was in the nap bed and part of circle time and roll call song.
I also had a book I got from a military thing I used to volunteer for. I helped watch young kids while parents did the Readiness classes before deployment and for the return events as well (when soldiers gather at the 30/60 days post return). At one of those events, they were handing out books and since I had my own upcoming deployment with a client I snagged one. It basically went like this "Over there, my Daddy (or mommy, there was a mommy version as well) does_____ just like I do at home".
So each page showed the soldiers doing every day things like playing with their friends (basketball game for them, and a daycare sort of setting for the kid), and sleeping (daddy in a bunk, and kid in his bedroom), brushing teeth, eating,etc. My daycare Mom loved this book so decided to take pictures of Daddy doing some of this stuff before he left and laminated them and put them around the house so her little man could see them.
I guess he would talk to daddys picture (of him with his toothbrush in hand smiling at the camera while standing in their bathroom), while he was in there brushing his own teeth, Another of daddy in his bedroom sitting in the rocking chair with a book, etc. She probably had a dozen around the house and some in the car. She had a small flip book of pictures for him in the diaper bag and one to keep in the car. Pictures were major with them and helped alot.
After Daddy deployed he took some pics of those simple things...brushing his teeth, eating, etc and emailed them to mom for the new flip book to have him compare. To see that daddy is still doing regular things, even tho hes far away working. Those were the things a child that young could understand.
Such simple things with some planning and they made such a HUGE difference!
There were so many changes in that year while he was gone. No more nuk (he was addicted), potty trained, big boy bed, no more sippy cups, etc, etc...but technology and comfort and "talking" to daddy all the time (thru the doll and skype) kept them more connected then I ever thought possible!
Best of luck!!