Sending messages to an iPhone without iMessage I need to send texts to my kids while they are away from Wi-Fi. I pay for a text message service through my carrier, but can't force my phone to send a text message instead of an iMessage with iOS 10.

So are all our iPhones incapable of sending text messages to people without data plans now?
On all of your iPhones go to Settings > Messages. 

You will see an option to Send as SMS. Toggle this on so your messages can be sent as normal text messages when the iMessage service is unavailable.

Hope this helps.