Lets start with UF.
UF freshman admits have to submit applications by Nov 1’st. Before that date, they can send in the $25 housing application fee. The date they submit the fee, set’s their priority date for on-campus housing. All test scores have to be submitted to UF before the end of December. Admissions are announced on the 2nd Friday in February. Merit and need-based aid usually goes out at the end of February, through the middle of March.
Freshman can apply to start in the Fall Semester or in Summer B term. Admissions seems a little less competitive for Summer B, so if you’re concerned about getting accepted, I would recommend applying for summer B. Admissions to Summer B, seems to be a bit easier at all of the Florida public universities (UCF, USF, UNF, FAU, FIU, etc.).
UF Online, UF PaCE and Innovation Academy, all seem to be a “bit” easier to get into than normal admissions (Fall and Summer B). IMHO, UF Online is best for someone looking to stay at home, need’s flexibility, and low cost (in-state tuition for UF Online is an awesome deal, with cost being closer to a local CC’s than an university). UF PaCE is best for those that know they will want to “transfer” to UF, and would rather take online classes than attend a local CC or another Florida university. .
Keep in mind that UF doesn’t consider major in admissions, so they do not need to pick a major (or can pick any major) when they apply to UF. It’s fairly easy to switch majors in your first year or two (this is the case at any Florida public university).
A 3.2 unweighted GPA is a little low, but if she’s taken mostly honor/AP/IB/AICE/Duel Enrollment type classes, her weighted GPA could be much higher. UF wants to see that you’ve taken the most rigorous schedule, at your school. UF also considers how she did compared to her peers in HS. If you’ve taken the most rigorous classes offered at your HS, and you’re in the top 10% (as an example), then that 3.2 GPA doesn’t look that bad. However, if you didn’t take rigorous classes, and are not in that top 10% range, the low GPA will likely be a problem.
UF uses holistic admissions (more on this in a bit), so other factors can help compensate for a lower (for UF) GPA. Still, holistic admissions can also seem a bit random at times, they should always apply to a few other schools as matches/safeties.
Based on a presentation by the UF admissions folks in 2014 (I think it still applies); UF’s holistic admissions is based on 50% “academics”, such as GPA, class rigor, the essay, and test scores (with test scores being least important factor). The other 50% is based on EC’s, leadership, volunteering, work history, etc. Strong EC’s are important at UF, but not on the same crazy level as Ivy’s and such. Strong EC’s could help compensation for weaker academic.
You want to make sure you’re doing something, every summer, such as volunteering, working, involved in EC’s, etc. Starting your own business is a great EC. 
For the sister, most of the large Florida publics would be a good choice (including UF). Most offer a wide range of majors (including history and psych), make it easier to explore majors in the first two years and are fairly affordable. Other than UF (which may be a reach) she should apply to a few of the other schools. Most are on “rolling” admissions, and will start making admissions decisions in October. It’s always nice to have at least one acceptance by November! For merit aid, it’s also important to apply early, while they still have funding. Try to apply before January to the rolling admissions schools.
For her brother, he needs to take rigorous classes (honor, AP’s, etc.), and try to raise his GPA. He should keep working on EC’s that interest him (such as running his small business). After looking at UF, if he’s interested in CS, he should look at FSU, UCF and USF. Several of the other publics also have solid CS programs. Florida Poly may also be an interesting option. It’s program should be accredited by the time he applies, and they may offer competitive merit scholarships.
For engineering, UCF and USF have a stronger program than FSU/FAMU. If he can get his GPA up to a 3.5 (and does well on the standardize test), some OOS schools become an option, such as the University of Alabama, thanks to generous merit scholarships
FSU/UCF/USF have gotten more competitive over the years. Picking at least one more school, as a safety, may also be a good idea. For example, my daughter who was interested in engineering, applied to UF, UCF and UNF (and then a few OOS schools).
Hope this helps!