Hi,
Good luck with everything!
The package you get will also be influenced by the industry sector your partner is in. Some industries have some seriously fantastic packages and other's are more mundane/usual (if I can put it that way!)
I've worked for USA companies and when staff have come over, by and large they got decent packages and some, usually more senior staff got more and more of the 'good' elements to packages. Friends in various industry sectors who've moved away from the UK have reported excellent/mundane packages as well.
Some of the package will be more individual - like the fact you mention you have a child's education to consider, so do evaluate everything you feel is important and discuss it with the employer to see what kind of 'deal/package' can be put together for you as a family.
From the other responses, there's plenty to consider and this forum does provide an excellent resource for pretty much anything you can think of to ask/find out about!
Cheers, DtM! West London & Slough UK!