which apps would you recommend?

Dh received a tablet which he can’t use and decided to let the dc use it. It is not compatible with Google Play or iTunes. We will have to get our apps from the Amazon App Store. Which apps would you recommend for:
cursive handwriting
spelling (I have a 2nd grader and a 5th grader) and
math (Neither child is on grade level; dd7 needs practice with adding through 20 and all subtraction; ds10 needs review of multiplication facts. Both could use work with fractions)

TIA,
Karen