I just used my regular road bike with the addition of a child seat (had a reversible 'Baby on Board/Vacancy' sign on the back). Low-rider front panniers added some carrying capacity and also improved the handling by putting some weight back on the front wheel. We used that commute setup until she was four and then converted our tandem to a kid-back arrangement. I'd drop her off and then ride the bike solo the rest of the way to work.