I'll chime in a little late with my own experience. We have a 1 1/2 year old and did have several good rides this past summer with him in a trailer (the recommendation in the US is to wait until age 1- we used the trailer for cross country skiing starting at 6 months, but waited until he was 1 before we attached it to a bike).

As an aside, we have a Chariot trailer and have been very happy with it. It's extremely well designed. He is forward facing but the set up and harness are great and it seems like it would be very hard for DS to be injured in anything other than a car accident.

This was our experience- overall, we've done a lot more cycling/exercising individually since our son was born. It's often just easier to take turns while the other watches our son. The down side is that we don't get to ride together as much and we both do shorter rides than we would have before our son was born, but it's just often easier for us to take turns and know we'll each get some exercise time. We had a lot of luck riding in the morning during my son's nap time between the ages of 12 and 14 months (though that said we never did ride as long as we used to). At about 14 months, he needed to drop the morning nap (and what this meant is that we couldn't let him fall asleep in the AM- if he did, he wouldn't be tired enough for a midday nap, and if he didn't get his midday nap, the end of the day was a complete disaster). So we had to give up the morning rides with the trailer at that point. While we could have ridden later in the day, we both simply prefer to exercise in the morning and opted for riding separately again. I expect we'll get out there again next summer when he's 2 and the nap schedule is a little different (it's currently winter here and we're not riding anyway).

So overall, you can have really good rides together with a trailer. But, you may need to be very flexible about timing, and probably won't be able to go as far as you used to. If you're set on doing lots of long rides with your husband, I'd look in to finding a good babysitter. Whatever you think you want to do, you may find that things change when you have the baby- as long as you and your husband are both committed to getting out together, it will happen- but you may find you're happy with shorter rides (at least for a few years).