The word grandfathers is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 21
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (70 words)
afghans, agendas, anthers, argents, arrange, dangers, darners, darters, dearths, defangs, defrags, dharnas, drafter, dragnet, eartags, engraft, errands, errants, farther, fathead, fathers, fraters, ganders, gardens, garners, garnets, garrets, garters, gathers, gnarred, gnashed, gnasher, gradate, graders, grafted, grafter, grander, granted, granter, graters, hafters, handers, handset, hangars, hangers, hardens, hardest, hatreds, narrate, rafters, rangers, ranters, redraft, redrags, regards, regraft, regrant, rehangs, retards, shafted, snarfed, stander, starred, strange, tanager, teargas, threads, traders, trashed, trasher