Personally I'd leave it another week at least, even down here in the South we have predicted night lows of 1 or 2 all this week so risk of slight frost.
I certainly would not put them out yet, I too have lot of 'plug' plants various types, but I am keeping them on windowsilll of unheated bedroom (gets afternoon sun) if it shines! My begonia plug plants are the slowest growing of my plants and are nowhere near size to plant out. Good Luck.