Ladakh, the Moonalnd
At first a great trip this one, you would love it. One thing-hope sept would not be too late as officially by sept 15th the roads close. Nevertheless, during this time the weather is at its best around Ladakh and Spiiti Valley.
Night stay at Jispa is fine but next day it would be difficult to make it to Leh. So instead stay the next night at Pang and then move to Leh, which is 110km from Pang.
Pangong Tso is only around 130km one way, but to get the best of Pangong,
Day 1 Leh-Tangstey, start around 9 or 10 am, reach Tangstey by late afternoon via Chang la.
Day 2-Leave Tangstey early in the morning aorund 7-8am, be at the lake by latest 9am. Spend some quality time there as the lake looks different as the sun rises in the sky, colorwise. Start from there by 1pm(if you have packed lucnh with you otherwise by 12pm, so that you get some time for lunch at Tangstey.) You will get Tourist Lodge and few small hotels at Tangstey to spend the night there.
Leave Tangstey around 3pm and reach Leh by late evening.
Same way you can do Nubra-Best time June-Aug. (http://www.tourism-of-india.com/nubravalley.html)
Day 1 Leh-Nubra Valley (150km from Leh). Start early, reach Khardungla by 9-10am, have tea or coffee there at the top. Leave for Nubra Valley . Stay the night at Diskit, you will find many guest houses and hotels too. (This accomodation you can book from Leh itself before leaving for Nubra)
Day 2-Move around Nubra Valley ie, Diskit, Panamik, etc. Panamik offers hot springs as well.
Day 3-Leave for Leh and reache Leh by late afternoon.
Leh-Tsomoriri-Manali (approx 240km)
Day 1-Start from Leh early morning around 5-6am, reach Tsomoriri by around evening or at the most late evening. Get the feel of the night and the lake, arrange for alpine tents before you leave from Leh. Guest houses are also available in the Tsomoriri village.
Day 2-If want to spend some time around you can do so, then start for Manali. By the end of the day reach Pang. Stay the night there.
Day 3-Start from Pang and reach Jispa or Keylong, stay overnight there.
Day 4-Start in the late morning and reach Manali by evening OR
Day 3-Start very very early in the morning from Pang and reach Manali by late evening or early night. Would be around 365km from Pang-Manali.
Now never worry about your kid, just be cautious and take proper precautions and be extra careful. Always drink bottled water, and not chilled, if possible slight luke warm. Also temp would be slightly cooler almost like Delhi's Dec-Jan. So carry proper woolens and other clothes. Try not to drive more tham 200km in the mountains, but the last phase like Pang-Manali, you could take a chance.
Also few tips do visit Alchi ang Thikshey monastery and if possible(if no constaints of days)do visit Lamayuru, the moonland. In my opinion the Manali-Leh road is better and safer than Srinagar-Leh. Though as you must know all adventure trips are not without risk factors.
What else?? I have taken a lot of your time, before I sign off "Wish you a great voyage to the top of the world"
Pragyan Paromita The beauty specially the full moon nights and night picnics and stroll to Shanti Stupa on a full-moon night and evenings spent at Pangong tso and many more.