You will likely get much more informed advice than from a 27 year old first time mum but I didn't want you to go unanswered.
I'd say the first thing is to get it straight in your own mind how you feel about the pregnancy. When you think about the next few months of pregnancy, how do you imagine yourself? Imagine coming home with a newborn and your 33 weeks off - how does that feel? It's hard to imagine a baby in the abstract - much easier to think about your life now with DH and your two DCs and think about a newborn baby fitting into that life. It also means that you will have a child at home for the next 18 years until you are nearly 60 - how does that feel? Are you excited about going through childcare, milestones, schools, exams, teenagers again in 15 years time, or apprehensive?
Next think about how you will feel if you terminate. Do you feel a weight of worry lifting off? Disappointment that you will not have another child? Both?
Next is to sit down with DH and discuss how he feels. It's his child, his life and his family that will be affected too. Is it just that he feels too old? Is there anything else? Hopefully if he feels you are open to his opinions and you haven't just made up your mind he will stop giving you the silent treatment which is just unacceptable at such an important time in your lives. It's your family so I'm not sure whether you would also talk to your DCs - some would, some wouldn't - you know your children best.
I would only then move on to logistics. Don't let the logistical issues make your mind up for you if you decide you'd like another baby. There are ways to make it work, as you found with your first child.
There's no shame in deciding that you just cannot bear to go through it all again - I know two women who have had late unexpected pregnancies when they thought they had already finished having children and just knew it wasn't for them. I remember asking one how she knew and she said the feeling with her first two children was one of overwhelming excitement and pleasure - but finding out about the last pregnancy was a feeling of depression, exhaustion and dread, so she knew that wasn't the right environment for her to have another child.
OTOH my MIL had her youngest son 11 years after my DH (same father) and said it was the most lovely wonderful surprise finding out she would be a mum again in her 40s, so she knew she wanted the pregnancy to continue.