Lezzles - here are a couple of good threads for reference
Darkerside ' s write up of last year family bike curious event
If you can wait to this year's event you should be able to pick up some good tips and see for yourself what the options are.
How I solved a similar problem
In answer to your specific question, I'd say you'd be best placed with a tagalong for the following reasons
1. You talk about the commute and running late. Makes me think there'll be limited opportunity for solo riding. Trailgators are best for when they can roam free.
2. Tagalongs tend to have 20" wheels compared to 14/16" wheels on starter bikes. There is a noticeable increase in rolling resistence from the smaller wheels - especially when you are riding it empty (& faster).
3. Trailgators require the towed bike to pull a small wheelie which puts the riders positioning slightly out from normal. Okay for short rides but gets them used to an odd position.
4. If you ride in all weathers the gunk from your rear wheel will spoil the towed bike and with the mileage on the rear hub it will aged pretty quickly.
The real problem comes when No2 arrives and you have to start looking at tandems...
Any further help needed just shout.