Wow, that's a lot of studying. What subject area are you going to read? And what college?
And its a good choice that you chose Oxford over cambridge (the latter is the evil village in Hot Fuzz).
Biking is definately better in Oxford than most other forms of transport, so as long as you are up for that, you will be fine. If you do want to venture outside Oxford, then the public transport is very good and you should be fine. (It is however fairly expensive, I am not sure how much it is in USA/Canada, but a single bus journey can be around 2 pounds, so a bike is definately cheaper. Trains are also very expensive, a single to London is £20)
As for the job prospect, i assume that she is a teacher (due to having a bachelor of education) so you might want to check up on the necessary requirements for being a teacher in the UK, because they are likely to be different than those in USA or Canada. But teachers do not really get high paid jobs here (as 90% of schools are state owned).
So, try and get one at a private school (I don't know if there are any in ox, but reason suggests there are bound to be some). If not that, then when going for state schools, go for grammar schools (they are selective school, and so are more likely to offer higher pay, and the children are going to be better).
Also, you and/or your wife can offer private tutoring, which is quite expensive in the UK, and you can get paid at least 20ish pounds per hour, and often more (depends on the subject/level it is being taught, and the supply/demand for it). However, as it is Oxford and so probably full of highly educated people, the supply for personal tutors may be saturated. Just put up an add on yellow pages and other websites, and see what comes.
Hope this helps.