I'm assuming you are not hiking the Inca Trail but will be taking the train? The tickets for the site entry are available for the rest of 2012. For 2013 you will probably be able to get them at the beginnng of the year. Exept for the highest demand weeks they should be readily available.

Permits for hiking the Inca Trail and (tickets including Huayna Picchu mountain) are another story.
Inka Trail tickets can sell out 3 or 4 months in advance. A good website for do-it-yourself Peru travel is www.andeantravelweb.com .

Easter Island falls under Chile so might get better response there.

Early to Mid-May is a nice time for MP. A combination of good weather, landscape that is still green, and less than peak crowds. Hikers come June to September for dry (but colder) weather. The "temporales" start in October and peak in Feb/March).

I think your wife would like Colca Canyon.

Thank you. My wife and her sister walked the 500 mile Camino in Northern Spain a few years ago, but I think I will take the train.

Re time in Easter Island - we were there 3 nights which gave us the following touring opportunities:

Arrival Day 1 mid day - 2 hour tour that afternoon
Day 2 - full day island tour
Day 3 - full day island tour
Day 4 - shopping and time in town; departure mid afternoon

We enjoyed Easter Island very much and could have stayed longer just to hang out, but in terms of seeing the sights 3 nights was sufficient time.

Link to our blog

http://lizandrichardsa.typepad.com/liz_and_richard_in_south_/easter_island/

Forgot to mention - LAN sometimes has a non stop flight from Lima to Easter Island (I think it's seasonally dependent) - that might be more convenient for you than going to Santiago.

I was in Easter Island for three days and could have happily stayed longer--but then, I had gorgeous weather. It does seem to make a difference in perspectives. You can see a fair amount in a small amount of time, though.

In case you haven't seen my trip report--it's got Peru in it, too, but just the Amazon bit: http://www.fodors.com/community/south-america/amy-l-peru-and-chile-a-possibly-over-enthusiastic-trip-report.cfm

I'm sure you know about going to the Sacred Valley first to acclimatize and so forth, but anyway this tour (holy horrors, Batman! It was a year that I didn't have planning time) worked well for me: http://www.fodors.com/community/south-america/peru-from-the-andes-to-the-amazon-trip-report.cfm

I didn't get altitude sickness on this one, and a year or two later in Lhasa--oh, yeah. (And in Ladakh, later yet, but not as bad as Tibet.) So that gradual thing is a plus for me, for sure. (Not that Machu Picchu is as elevated as Lhasa, but still...)

Thank you all. We will be flying from Lima rather than Santiago.

We will not hike the Inca trail, but we did some easy hiking in the Alps and the elevation did not bother us there. It seems to be roughly the same.

Is there any biological reason the two would differ?

My Alpine hiking didn't go much above 7,000 feet, I don't think, (mostly in Hasliberg region) so I can't comment on that one; MP is near to 8,000, which seems to be the "magic number" for possibility of altitude sickness. Actually, I'm usually okay up to about 10,000, and you might be fine in MP; if you go on to Cusco, of course, you'd be a lot higher.

I really kinda like Lima airport; I've spend enough time there! The domestic terminal is very cozy; if you get in on a late night flight and have an early one out, it's easy to sleep.

Thanks you Amy.

I doubt you will have altitude problems. But if you do, good luck with them.

I doubt you will have altitude problems. But if you do, good luck with them.

You know I already have an attitude problem.

I'm in the Lima airport as I write...just spent a few days in Lima. Didn't get to MP this time, but found Lima to have some interesting sights.