What are the options then?
There's the long tail bike with seat, like the Xtracycle. Now, I haven't ridden a longtail bike in a while, but they can be very heavy if it's all one bike frame (Yuba), and wobbly if it's an added attachment (Xtracycle) and you're carrying a lot of weight. These are popular around beaches, and bumming around town, and though people do use them for long touring and may like them, they can be cumbersome, and Neva wouldn't be able to pedal. They also are a bit of an investment, so it might be worth considering a tandem if you're willing to spend the extra money and have the extra frame weight.
Holds a lot of gear
Heavy and cumbersome, difficult to travel with
Has a seat and harness when child wants to sleep (extra cost)
Neva can’t pedal
|Good for around town, small day rides|
Need to either redo whole bike, or buy new bike ($500-$1300)
The tandem is a possibility, but a very large investment, so we would have to calculate out realistically how many years we might be able to get out of a set up like that. I like the idea of a tandem, but I would want Neva to be able to stop pedaling when she wanted to, and that set up is also costly. It could be a very good set-up, but it would need (off-road capable) tandem + kidback (so she could reach the pedals)
Just like a regular bike, but longer (ie. familiar for repairs, can transfer rack/pannier set up, etc.)
Cumbersome, difficult to travel with (even with S&S couplers, which add $600-$1000 to cost of bike)
Seat and harness potential
Cost : $3500 (bike) + $300 (kidback) + $60 (backrest) + etc.
Neva can pedal for years if she wants to
Most trail-a-bikes aren't meant for off-road use, and don't have shifting capabilities, though a few do, like the Burley Piccolo which is a 7-speed, and lets the child learn about how to shift. The Piccolo is also unique in that it attaches to an included rack instead of to the seat post. This means that you will be able to mount your panniers without worrying about clearance from the hitch arm. The concern I might have is how the trail-a-bike might lean if she does nod off and if the hitch is made for that kind of use.
Tracks similarly to a trailer, fits child with adjustable seat and handlebars, can add seat
Short lifespan, depending on how quickly child grows (though possibly a good 3 years)
Has shifting capabilities for learning and rack so you don’t lose storage options (with Piccolo)
Leaning potential for when the child is sleeping
Detachable, small, light (aluminum) potentially easier to travel with
Unknown capabilities for long, off-road trips
Reasonable price : $359 + backrest