If they decide to do university and have to do a year or two college prep then that's fine. If they decide to go straight into workforce that's fine too.
I know it sounds like we are fixated on the education thing but you don't seem to understand.
Neither will get into uni without qualifications, and nor will they be able to work without them.
If your eldest enrolls in college with no qualifications then she will have to do a level one course, lasting a year, then a level 2 course lasting 1 or 2 years then a two year level 3 course.
If she gets her high school diploma she can at least go on to a level 3 course and have a stab at a descent uni.
As for fees being cheep - that's the cost for someone permanently resident in the UK who has been here 3 years, you might be charged international fees that are much higher and dd might not get any help with living costs.
Link to Leicester uni for computer science for younger child. How much coding has she already done?
le.ac.uk/courses/computer-science-bsc
They want GCSE maths grade B - if your youngest can get that then great, but the chances are she will not, not because of lack of ability just because she will be starting so far behind in content.
The 'US requirement' mean little to me but this is a direct quote.
For entry to the first year of a Bachelors degree you will need a High School Diploma with at least a grade C average together with SATR (Math, Critical Reading and Writing) with a minimum score of 550 in each and three Advanced Placement exams. The AP grades needed will vary depending on the degree that you wish to study but grades 4 or 5 would be a typical requirement. You may also require specific subjects for some degrees.
If you are studying A-levels or the International Baccalaureate (IB) then you can begin from the first year of a Bachelors degree. Please see our individual course pages for entry requirements
If you have already completed the first year of an undergraduate degree at a university in the USA , you may be considered for entry to the first year of a Bachelors degree. Law students only: Please note that you can only start from the first year of a Law degree. No credit transfer or exemptions are given.