This is such a tricky one.
Firstly, you sound quite sure you'd prefer to terminate, but have you taken a day or two to let it sink in? Fwiw I do think that you should put a lot by your gut reaction on finding out you are pregnant, but it does help to stop and think a little bit and take a day or so to be sure.
If you are sure you are not in an emotional or financial place to have another child then it is more your decision than his, far, far more - your body, your baby. So while I would never argue that a decent man should have his wishes ignored, it is still the woman's decision at the end of the day. So if you want a termination, then you have a termination.
Having said that, if he is a decent man, it seems slightly wrong to never tell him about this pregnancy. And can I ask what makes you so sure he will try to talk you round? IMO there is a big difference between knowing a man would prefer to have the child, and thinking a man will try to some way manipulate you (consciously or unconsciously) into having a baby you don't want.
If it is the former, are you certain that he won't respect your decision?
If it is the latter, would that make you reconsider your decision to be with him?
I kept my termination secret at the time from pretty much everyone. Even though I was 100% certain and DP was too, it was still an emotional time for both of us and I can't imagine trying to keep that emotion (hormonal, tired, all that) secret from him. I also have a very old, close friend who I haven't told and honestly, the amount of times I have almost said something by accident. It would be a very big secret to keep from someone you see a lot.
The termination, if you want it, is entirely your choice. But on the balance of things, I would say that not talking to him would be a big problem.