Vallemaggia is nice.
My elder daughter lives/works in Bignasco, there's some camping along the way, and nice rides in Val Bavona, to Bosco Gurin (from Cevio), the valley up past Fusio to Naret, etc.
At the end of Val Bavona, there is a cable car to San Carlo, restaurant/hotel/hiking up top.
At Naret, there are several lakes, nice spot for a picnic and/or hiking. Steep, narrow road full of sheep, though.
At Bignasco, there is a nice waterfall/swimming hole (plus a pool and park).
At Ponte Brolla, you can head up the Centovalli, Val Onsernone, etc.
Good area for a bunch of day trips, my wife and I often go and spend a few nights there (Cevio or Bignasco, though now we can crash at my daughter's), though almost every time I stay up there, the cops phone me to ask if my bike is stolen (I guess they find it strange that people from Ticino go there for several nights in August!