UPES

For CS, its ranking is not that good. But for petroleum engineering, its ranking is 3rd all over India. Still, CS branch gets good placements in UPES.
But at last, it's up to you.

Among these colleges I will prefer UPES for you in terms of placements and study. You can check placements on their official websites.

I will prefer IPES. It placements are good as comparison to others. And study is also well mannered.

I don't have any idea about IPU.
If your son has 112 marks in JEE having general category, then he might not get any good NITs easily.
He can go for other private colleges.

Counselling is starting from 31 may. So there are very less chances that you will get petroleum branch. There are only 20-25% chances for getting petroleum engineering. But you can try for it.

Government colleges have more reputation than private colleges. But if you are looking for good placement, then some government colleges don't provide good placements (not all of them).
And there is also mass recruitment in all colleges. So you have to be unique if you want a good package. UPES provides good placements. But mass recruitment is also present in UPES.
VM provided more than 15 LPA. Microsoft gave an offer of 11 LPA.

I don't know much about MAIT, Delhi but in UPES it is good. There are several sub branches for CS. It's up to you which branch you will choose. Placements in UPES is also good. Faculty is also experienced which will give you full support. The highest package offered was around 27 LPA. Top recruiters are Microsoft, VMware, dell, LNT, IBM.

UPES is a good college to pursue BCA. You can go for the same college. There are many other colleges in Dehradun like:
Doon Business School
UIT
Dolphin Institute
ICFAI
You can compare them but you'll end up choosing UPES or DBS.