Originally Posted by HaleiwaFlyer

Definitely do-able, but the first trip is great to check out places that you like and don't like. There is just so much to do in Peru and each city, and there won't be enough time for everything. As for altitude sickness, consult with the pediatrician/physician for possible medications and tips/hints.

For the Cusco flights, take the early flights, as delays/cancellations may occur in the afternoon due to weather.

Make sure you reserve your tickets to Machu Picchu early ( book on the government site), and chose the hike you would like to do: Machu Picchu Ruins + Huayana Picchu (think of the photos of the Mt. top, looking down on the ruins) vs Macchu Picchu Mountain. Plan to choose only one mountain and the ruins. Also plan to pick up tickets before the bus ride up from Aqua Caliente to the ruins, and plan on purchasing tickets for the bus rides ahead.

Tambo del Inka is awesome, and one of my favorite resorts. You can spend a lot of time at Sacred Valley exploring the different ruins. Sacsayhuaman has lots of ruins around it too, don't miss out on the natural slide in the backside.

Have a great trip.