Depending on your child's size, you may not be able to buy a helmet to fit until after a year. I knew that extra-small helmets are very hard to come by in the US so I bought one listed on the helmets.org site -- it was a Vigor L'il Tyke, but those are since discontinued. They do have others listed there this year. It fits my kid fine but she does not have a small head.

I am in a moms-and-babies cycling club and nobody's pediatrician recommended a helmet before one year. The helmet is a danger on its own at that age, unfortunately.

That said, your route sounds fine to me, CyclaSutra. The Chariot trailer has great shocks but the baby really needs to be about 25 pounds to get any use out of them -- at a year my baby is still about 8 pounds too light, so she doesn't like bumps. She also does not like speed. My husband has found that if he goes over 15 miles an hour, she is pretty likely to cry. But she is getting more tolerant of both speeds and bumps as she's gotten bigger.

When your baby is a little bigger, I highly recommend this MP3 player as the best trailer toy ever. It has a little mono speaker so you don't use the headphones, obviously, and the baby can have his or her own music back there! We usually barely even hear it (we hear her "singing" instead) but it has really helped to keep her happy in the trailer. We introduced it at the same time that we introduced the helmet and it was a completely smooth transition, no fussing at all.

Congratulations.