Here’s an example:
Student: Thanks for dinner, it was great! I’m going to take a quick shower and then I am leaving for New York with my friends. I’ll be back on Sunday night.
Host Father: Glad you enjoyed the meal. Have fun this weekend, be careful, and keep in touch! Give us a call sometime on Sunday to let us know when you will be coming back.
Nowadays we have many ways of “keeping in touch”. You can text, email, or call your host family to communicate with them. Let them know where you will be, whether you will be home for meals, and what time you plan to return in the evening.