There are multiple collections of Mickey, Donald, Goofy, Chip and Dale, etc. shorts now available on DVD, and Toon Disney still airs House of Mouse. Mickey is also highly visible in just about every aspect of products and services, from TV and video to coloring books, toys, games and everything in between. The only reason a child wouldn't know who Mickey is would be a result of how much he or she is exposed to by his or her parents. The OP has nothing to worry about, and if you want to share more Mickey with your little ones, it's entirely up to you.
No need to panic.
I wouldn't expect any new hand-drawn animated features in a theatrical release from Disney in less than 3-5 years, which is the average length of production for that kind of a film. John Lasseter could certainly greenlight a 2-D production within a year, but even his magical powers are subject to the realities of time and space.