I also use flashcards to help with the rote math homework.
I do recommend to my children and my students that they consider doing one thing I did as a kid, namely fill out a multiplication table (the one I did in childhood was 30 × 30) by hand by hand calculation. I did that in odd moments during the school day and kept the table stashed in my desk between moments of working on it. Filling in a multiplication table helps learners notice number patterns (it made me very conscious of perfect squares, for example) and produces a tangible accomplishment at the end.
For a child the age of your child, I enthusiastically recommend the Miquon Math materials,[2] which are inexpensive and take a thoughtful, playful approach informed by higher mathematics for learning much of the content of the first several years of elementary mathematics. All you need to use with the Miquon Math books are Cuisenaire rods,[3] which are available from various sellers and are a fun plaything in themselves.
I did the multiplication as a child myself, only 20x20. I've also tasked him with the table, 10x10.
But I enjoy solving problems, e.g., http://publicsphere.org/2014/02/07/exercise/ http://publicsphere.org/2014/01/04/fibrations/ http://publicsphere.org/2013/12/23/markets-and-market-games/ http://publicsphere.org/2013/12/14/elementary-equivalence/ http://publicsphere.org/2013/12/12/another-problem/ http://publicsphere.org/2013/12/08/problems/
I have many more in password-protected blogs, notes, etc.
This morning a friend informed me about Oppia https://www.oppia.org/. I took a few minutes to solve their introductory example, Euler Project Problem 1 (Question: What is the sum of all the multiples of 3 or 5 below 1000?). I did this in Mathematica by combining inclusion-exclusion (expressed via indicator functions if you like) with little Gauss's formula for summing the integers from 1 to n.
SumN35[n_] := 3SumN[Floor[n/3]] + 5SumN[Floor[n/5]] - 15*SumN[Floor[n/15]] where SumN[n_] := Binomial[n + 1, 2]
I got SumN35[999] = 233168.
[OT lamentation ahead] Unfortunately, in my experience, employers don't seem to value this activity--at least I tend not to impress them as a confident person who will passionately defend his answers until shown wrong. I don't have the personality, patience and energy for this kind of bravado. (I have an acquaintance who has the requisite unaesthetic attitude, who is not more intelligent that I am and who landed a job at Google.) I tend to have inspirations that come from nowhere that I have to go back and reason about. The act of convincing yourself that a correct answer is really correct can sound like a lack of confidence to some individuals. To me, projecting confidence requires extraneous cognitive load, but I can be confident for an additional charge.]
If you tell me that using flash cards is morally wrong, or if you have a theory of learning that invalidates their use, I won't argue.