There are some angles you can pursue with additional activities like logic puzzles and games but my feeling is that at this level it makes the most sense to just finish mastering basic arithmetic i.e. move on to multiplication/division etc. There's a lot more opportunity for enrichment after that's completed. This can be done via many routes and I don't think you have to worry about paying attention to standards while doing so.
Last edited by BenjaminL; 10/10/14 12:46 PM. Reason: additional expl.