What about less problems (looks easier) but more engaging.
Take a look at
Primary Grade Challenge Math
Edward D. Zaccaro
He also has like 3 other problem solving books. In each book there is a lesson and then about 3 or 4 (I forget) different sets of questions to answer. There are only about 4 questions per set and each set is a different level with the last one being like the Einstein level. You could do the first level set the first time through the book and then go back a second time and do the higher levels. My boys found the book very engaging.
