I had a similar choice although I was in my first trimester, which is apparently a worse time due to the baby's formation... and also had to do the research all myself, which I couldn't quite believe, their only advice was to cancel the trip. I tried talking to a really good travel clinic but they wanted to see me in London, you could always try that.
After reading up, talking to a GP friend (who said she couldn't possibly advise not taking anything) and talking with the person organising my travel in Zambia, I decided not to take anything and be super careful. I know it isn't entirely helpful, but I figured plenty of African women do have babies and cope.
I used child insect repellant through the day (not really relevant for malaria) then much stronger stuff at night, was paranoid about tucking my socks into trousers etc. and used really strong stuff (as strong as I could find) to fumigate my room every evening, and was religious about tucking my mosquito net under me in bed. I didn't get bitten once, which has never happened on previous trips.
On speaking to a woman living there she said that malaria was really common and the treatment actually much easier than they make out in the UK, because people will recognise the signs very quickly there. On the other hand, she said the only two times she had malaria were both when she was pregnant. I think that's in part because of a weakened immune system, and second because of how your body is warmer and you produce more carbon dioxide, both of the ways the female mosquitoes find you.
I'm afraid the one thing I can't do is reassure you that it all turned out fine, as I MC'd the pregnancy. To be honest, you have to make a decision that is right for you and that you can live with... and no amount of advice can help with that. But I'm in total agreement that GPs are really not very helpful in this situation. If you are moving there though, anti-malarials won't ever be a long term option and you'll have to get used to the paranoia for protecting your new baby.
Sorry I can't give a more definitive answer, but good luck with your trip and pregnancy.