Thats great Luke, keep it up. stay consistent. even when they dont respond.
For me personally, when dealing with my daughter (8 y.o.) i tend to forget to think like a child. instead i think about how i would like it, in my adult mind. but thats wrong. she loves the fart jokes, so fart jokes it is.
kids, teens, like it light, they want to feel independent, so a quick simple txt sometimes carries more affect than a long well written letter on fancy paper.
over time, the little txts, and pics will add up. and you'll get home after the month and your relationship with them will be that much further.
"In a ham and eggs breakfast, the hen is involved, but the pig is committed".