Well - I'm sure you know that this is a lot trickier to get right than just first letter of first and last name - since a last name like O'Brian or McAfee starts getting pretty tricky. But you could use translate and substring functions to try this - like:
concat(translate(substring(my:FirstName, 1, 1), "abcdefghijklmnopqrstuvwxyz", "ABCDEFGHIJKLMNOPQRSTUVWXYZ"), substring(my:FirstName, 2), " ", translate(substring(my:LastName, 1, 1), "abcdefghijklmnopqrstuvwxyz", "ABCDEFGHIJKLMNOPQRSTUVWXYZ"), substring(my:LastName, 2))
The above assumes that the first name and last name are in different fields. This would be different if they were in the same field - you'd probably need to use substring-before and substring-after to get the text before and after the first space and cross your fingers no one is named Mary Ann.