Mollymct, that is great. You needd to decide firstly, how big you want this to be,currently it will be 24"X 40" as a finished centre. I would put a solid color border of about2"next, followed by a 5"-^' patterned border, using a single fabric from the blocks, if there's any left, or a scrappy border made from all the fabrics used in the centre.
Whatever you decide, it's looking good, and 4 year olds love quilts, especially when it's all theirs.
Goodluck with the rest of it.