To do that trip, I'd pick my window of weather very carefully. The seas can be pretty uncomfortable around the islands at anything over a f3, especially wind against tide. IMHO it'd be too much for there and back in one day, so I'd suggest you'd be looking for two consecutice days of good weather. Not something we've had much of this year
I often do Jersey to Alderney (35nm) and that becomes very tiring when its a bit lumpy and you're not only trying to dodge the waves, but also the pot markers and any other boats that may be about.