Aaron has posted many good points on this thread, especially the advice regarding doing just Slide & Hunter because they are 4K. I want to second the suggestion that you also do Wittenburg and Cornell with Slide. This is a classic and truly one of the best hikes in the Catskills. It offers everything from deciduous forest to steep rocky climbs, ladders, scrambles, and open scenic viewpoints.
The same goes for Hunter. This one can be done by a fairly easy jeep road, or by the much steeper Devil's Path (to the connector trail). It can also be climbed by the Becker Hollow Trail or from Diamond Notch. Aaron's suggestion to bushwhack SW Hunter is a great one. Or, for those who decide to take the jeep road, a bushwhack up Rusk Mountain is another option to make for a longer and more interesting day. And for the very ambitious, you can do all three!
The loop from North Lake on the Escarpment Trail (and Kaaterskill Falls) is a good hike, too. Very interesting and scenic area, but not as challenging. I think the "die-hards" may prefer a section of the Devil's Path. Indian Head and Twin for the "3s", then add Sugarloaf and Plateau for the "4s".
Since there will be a lot of people coming with a wide range of fitness levels, I think a lot depends on how people feel after the first day and how much they want to push themselves. I'm sure there will be at least 2 or 3 different groups of us doing different hikes. For those of us that are very familiar with these mountains, it will be a lot of fun sharing the trails with those who have not yet experienced all the magnificence that the Catskills have to offer. Bottom line - - - we'll give you some ideas for hikes, but no matter what you decide, you too will fall in love with the Catskills. After volunteering last weekend for the Devil's Path Charity Hike and meeting so many wonderful people from VFTT, I can't wait to meet even more of you ......... and this time I get to hike too! It will be a pleasure.