The car trip is about 300km one way. You can budget 4 hours from the time you get rolling in Ottawa to the time everyone has their boots and packs on and is ready to hit the trail.
There are two equally good routes. One is down highway 416, and crossing the border at Ogdensburg. The other is highway 417, highway 138, cross border at Cornwall/Massena. The goal is Keene Valley, which is at the bottom right corner of this map:
The trailhead is in "The Garden", a hiker parking lot near Keene Valley. This holds about 60 cars and costs about $5-7 per car. It gets full, and if it does, one has to park quite a bit further away. The book says 1.6 miles further (2.6km). However I think there is now an overflow parking lot out by the highway and a shuttle bus. None of this is an issue if one arrives late in the day for an overnight campout, as the day hikers are leaving by then.
From the Garden, it is an easy 3.5 mile (5.6km) hike to Johns Brook Lodge. I think the lodge offers accommodations for 24 in two bunk rooms and also offers meals. More interesting for groups are two cottages, one for six people and one for twelve, in the near vicinity. The cottages are nice and have gas cooking and light. It is essential to reserve any of these accommodations well in advance. As for the cost, the one time I was in the 6-person cottage it cost $80 (US) for the night. Split six ways it's a pretty good deal.
The cottages have bunk beds with basic plastic-covered mattresses. Whatever else you need, sleeping bag, sheet, pillow or whatever, you have to bring. I recall there was a good selection of dishes and pots and cutlery. Water can be gotten from a clear mountain brook about 50m away. It must be boiled or treated for safety though.
The actual hike would be done the next morning. Since you don't want to lug your sleeping stuff etc. up the mountain, and the cottage must be vacated by noon or so, there is no choice but to stash your stuff somewhere. In the past we stuck it under the cottage's porch. You want good stuff sacks for this, or leave your pack and take a light knapsack up the mountain.
The hike itself goes over a great mountain ridge with three actual summits. It is outlined in this map. You can click on it to get a higher resolution version without the yellow dots. You can see a bigger view including Keene Valley here.
The hike can be done in either direction. If done in the (otherwise preferable) clockwise direction, the disadavantage is a longer slog (on tired feet) back to the car after coming down the spectacular west side of Gothics.
Either way it should be possible to have breakfast, do the hike, head back to the car and return to Ottawa at a civilized hour. Depending on the time it is often tempting to seek out a restaurant in Lake Placid or Saranac Lake after the hike though and with 3 hours left to drive it can get late. Why so hungry? Well at my body weight and aerobic efficiency I estimate over 4000 food calories burned to lug my sorry carcass up one of those mountains.
The main loop sounds short at only 8.5 miles (13.6km) with light day packs. It is however strenuous because of the elevation changes as you can see from the topographical map. An average speed of 2km/h for the whole thing (including stops) would be quite reasonable.
This is of course followed by the reasonably flat 3.5 miles (5.6km) back to the car with all your stuff.
Wear sturdy boots. A sprained ankle is a real pain when you have 3000ft of elevation to lose and 12km to go back to the car. Trust me, I've been there.
Plan on carrying 3L of liquid up the mountain. If it's a hot day, carry all you can.
Bring a headlamp or flashlight that is good enough to walk in the woods by. Not a mini mag-lite powered by two AA cells. It's useful for going to the can in the night and it's an essential backup during the short fall days, in case the hike goes slower than planned and it gets dark before you get to the car.
Gothics seen from Haystack Mountain (i.e. from southwest)
North face of Gothics, in early spring
The west side of Gothics. That's the trail on the left there.
If only the trails were this nice all the time. That's Gothics in the distance, just over Brian's head.
Thanks to my friend Andrew for the photos from his collection.