The books were:
The Mouse That Roared 1955 New York: William Morrow
Beware of the Mouse 1958 New York: Putnam
The Mouse on the Moon 1962 New York: William Morrow
The Mouse on Wall Street 1969 New York: William Morrow
The Mouse that Saved the West 1981 New York: William Morrow

It took me AWHILE to find and read them all.. and I NEVER managed to find the last one.