I'm 45 and 21+weeks pregnant. I've had miscarriages before, but no children. So I think you'd be in a better position than I was. The risks are there, but not overwhelming. For instance, based on my age alone, I was given a 1:11 risk of trisomy 13 and 18 and 1:17 for downs. I had the materniT21 test at 13 weeks and everything came back fine. My high risk OB did say that women our age have a greater chance of stillbirth the closer we get to term, so he'll see me more often...2 or 3x's a week...I actually looked that up on the internet and the risk is there but it's not a huge one. He also said there was a risk of fetal growth restriction, but so far my baby is measuring 3 days ahead and weight is a bit ahead as well.
I think that's all he told me. I don't think the risks outweigh the blessing, so I'd say go for it. I wish you all the best luck!!
The fact that you had 2 kids before without complications is a good sign! Many ladies here had successful pregnancies after 45 although your ob may monitor you more closely this time around. For example, my ob would not let a woman after 40 go beynd 40 weeks. There are graeter risks of placenta failure, etc. These risks are still small though.
Good luck!