Wanaka is a stone's throw away from Queenstown (well, 100km or so) but it's worth visiting for so many reasons. I've been in summer and in winter and whilst the place is bustling with tourists, pretty much, at all times, it's a must-see destination for any New Zealand adventure.
There are heaps of places to stay - many within walking distance to the lake itself. You'll be spoilt for choice with where to eat and, depending on where you stay, lots of places offer discount vouchers to various establishments so be sure to ask about those when you check in.
Beautiful lakes, a seemingly never-ending mountain range and enough tracks and trails to keep you busy for days. Of course, in winter there's the added bonus of snow-capped mountains but summer is a time for lake-side sunbathing. Can't actually decide which I prefer.
My top tips would be hiking Grandview Mountain, Roy's Peak or Mount Iron or simply strolling around the lake if you're after something less adventurous. Visit 'That Wanaka Tree' to recreate a famous photography. Try stand-up paddle-boarding, hire a bicycle and see where you end up and go wine tasting at one of the local wineries. Whatever you do, you'll have the best time in an idyllic setting.