Mmmm, yes, Europe. (nods sagely)
I think front seats only work really great with a long step-through frame and swept handlebars. They might be ok with a US-standard mountain bike if you are ok with cowboy starts and it doesn't run into your chest. If you want a front seat, go for a Yepp or Bobike, probably. I didn't try a Weeride because it would obviously require cowboy starts and didn't get to try an iBert. I had a Thule and it was, IMO,
defective in design even though other people give it
glowing reviews.
Trailers work great and have minimal impact on how your bike handles, they are just
so much work.
I found a back seat to be much easier to deal with as soon as he was big enough. I like the
Blackburn Copilot brand, they come with a standard type rear rack and unlatch easily so you can use it for panniers or whatever. The previous color has been on
blowout clearance for a while so if you can still find it, I say go for it.