I'm pretty sure my DD loved both Penrose the Mathematical Cat and The Number Devil before she had mastered addition. They explore the nature of numbers with fantastical stories and characters. Penrose poses problems, while the Number Devil just tells silly stories. As long as she can follow along while you work the problems, they may be worthwhile. Both of them are more "bedtime stories for the mathy" than curricula.
DD still keeps a whiteboard by her bed for working math problems before she goes to sleep. Makes me smile.
