Changing your surname 😳

Cherwee
Hi all, so I got a question and just wanted some of your opinions, babies asleep so I'm thinking too much with all this quiet around me😜
I have been divorced and have been with my partner now for 3yrs and we have a super cute beautiful 5 month old baby boy together, and also I have a gorgeous nearly 6yr old daughter from my previous marriage. 
My partner has also been married.
We have talked about marriage again, but neither of us really want to get married again but at the same time we both keep talking about it and I guess we really do want too( we just want to elope the kids there and no big wedding this time round if we go decide to get married) 
  I think what's the point, we love each other so much so do we really need to get married ❤️😳
I look at my Medicare card and there 3 different surnames on it, mine, my daughter and my sons, I thought about changing my surname to his, which he really would want for me to do if we got married.
Ok ok so my question is, if you've previously been married did you change your surname, then change it back and have you got married again, and change your surname again?? 
I'd like to know from both people that have been in this position and also from all others perspectives too. 
Thanks all for your input 💃☺️