We really enjoyed having our two kids in ICS Lima. It is a smaller school with good quality teachers (almost all Americans), and a very caring atmosphere. Obviously, you need to be comfortable with the Christian aspect of the school because it is quite strong. We moved both kids out when they were 13 though, since the upper grades did not have many kids and the options and electives get a little thin. Another drawback from our perspective was that there is a fairly high rotation of children at the school. Most seem to stay 3 to 4 years athe most. ON the positive side, they have small class sizes ( I think 15 is max, and we found on average of 7 or 8 during our time there). On the negative side, athletic facilities are lacking. Overall though, it is an excellent school, particularly if you are only going to be here for a few years, you value an English language education, and you live in Miraflores or San Isidro.
We also had experience with Peruano Britanico. Note: if you live in Miraflores, it is a one hour commute there and back most days. It is an IB school, and they have invested pretty heavily in facilites over the past few years. The education is good overall, and the administration was top notch. Classes are fairly large though, and the school is geared towards self-motivated academic achievers. Markham is a more established school and more expensive than PB. Note that they have two campuses though, so your kids would be split up, and you would be drivin g to two locations, not one.
In my view, Roosevelt is the creme de la creme. I have never met a Roosevelt teacher or administrator who did not impress me. Downside, it's the most expensive school in Peru, and not only are you paying high tuition, the entry quota is a killer. Now, if your husband's company is paying, lucky you, otherwise, do some number crunching.
Drop me a PM if you need some more information.