Apple Watch SE second generation

I just got my son an Apple Watch. it has its own cellular line, he can make texts calls. it's not paired to an iPhone. I did have to use my iPhone to set it up. whenever I text him, on my end, the messages come up as green. I also cannot see his location. my husband can text fine and it goes through as an imessage. he can see his location also but it is not a live location. I tried resetting his watch but when I text it still comes up as an sms message rather than iMessage and still can't see his location. its currently going through an update but I doubt that will fix the issue. any ideas on what could possibly be going wrong? I was beginning to wonder maybe because I set up his watch through my phone its linked somehow? im not sure.