How old are they?
I'm guessing school age because you mentioned notes? Maybe bake them something special before you leave as a surprise. Or, if they watch movies / DVDs then buy / rent / borrow a couple of things for them. How about something you loved at their age?
It'll be quite a climate change this time of year. Have fun!
Empty-nesting SAHM to DS1 (1989), DS2 (1992), and an overachieving mother (1930). Married to DH since 1986.