One of Simon Heffer‘s pet hates is the use of singular they: “Being a pedant,” he writes, “I regard [its use] unacceptable” (2010:110). Unacceptable or not, singular they, as Mittins et al. point out in Attitudes to English Usage (1970!), has been in use since at least the fifteenth century (p. 102). If even someone like Jane Austen uses it, how can it be unacceptable?
Source: Gretchen McCulloch
So well done, IKEA (and thanks to Gretchen McCulloch for tweeting about it), for adopting it and helping singular they become more acceptable, even, hopefully, to writers like Simon Heffer (but then perhaps he doesn’t shop at IKEA).
Now what I’d also like to know if if IKEA splits infinitives, misplaces only and uses literally as a plain intensifier. Let us have more images like this!
Bridging the Unbridgeable 
Just looking at this blog for the first time after being directed to it by some correspondence I was having. This particular question – speaking with my editorial hat – is a prime example where rephrasing would avoid the awkward use of the ‘singular their’ …eg This card game is a fun way for children to train their memory as well as their visual and social skills.
Often looking at a different way of saying something gets over this kind of problem – general editorial point is to self-edit and simplify where possible.
I know! I myself would have written “your children” rather than “your child”, which seems funny to me. Thanks for your comment!