Reese Witherspoon is a doting mother to three children, two of whom, Ava and Deacon, she shares with ex-husband Ryan Philippe, and another, Tennessee, that she shares with husband Jim Toth.MORE: Reese Witherspoon stuns in dreamy beach photo on last day of vacationOn Saturday, the Legally Blonde star shared a rare picture of Ava and Deacon, and posted the most heartfelt tribute.WATCH: Reese Witherspoon's children make surprise appearance in fun video"Gosh, I'm lucky to be their mom," she penned