You've asked a very open ended question that will result in 100's of opinions so we need to narrow down your inquiry a bit. What type of sailing do you intend to do? Where? Long-distance cruising or island hopping or local? How many people do you usually transport? How much do you want to spend? Rigid or inflatable? How do you envision storage? What size is the mothership?
Hope this helps,
I would suggest that you choose a dinghy to build that is at least adaptable to a sailing version (assuming you're primarily talking about a tender) A sailing dinghy can do double duty as a small tender and provide hours of enjoyment and diversion for young and old alike.