I had that routine years ago when our daughter was small. I'd take her to daycare which was a few miles past where I worked and then ride back to work. The first few years we used a rear child seat on the back of my road bike. No problem with a high top tube - just swing your leg over the front of the bike instead of the back (practice first without the kid aboard). Those 'Baby on Board' signs were popular on cars at the time so I attached one to the back of the chiild seat. I put 'Vacancy' on the back and would flip it over after dropping her off.

When she was about 3.5 we switched to using our tandem. I got a Phil Wood clamp-on bottom bracket that attached partway up the stoker's seat tube to let her reach the pedals. Instead of the usual chain arrangement where the stoker's crankset drives the rear wheel cogs, I put on an extra-long chain that went all the way from the front crankset to the rear wheel. Worked fine and eliminated any chainline issues with cross-over gear combinations. Used the tandem through kindergarten and then the school system offered bus transportation and an after-school program so I didn't need to take her anymore.

I think either a two-wheel trailer or a child-seat would be feasible for you. We did use a trailer for awhile, but I found that it was harder to communicate while riding. But I do sometimes use a siimilar trailer for touring and have never had any issues in traffic - even in urban centers. If you do go with the bakfiet approach above, I'd recommend the two-wheel CargoBike over the CargoTrike for better handling and maneuverability.