Jay's plan to use beam pockets in the front wall will work fine. Dbl. top plates with no additional structure supporting a roof over a SIX foot span (as per Tester101's first suggestion) is entirely inadequate. Whether a 2x beam on edge is adequate, and how deep it is, depends on what the roof snowload is, if any.
There are also hardware beam hangers available that support the end of the beam and are nailed or bolted to the supporting studs in the front wall, eliminating the need to frame pockets. Tester101's second suggestion to use a ledger to support the beam end is a viable idea, but the connection of the ledger under the beam, into the studs needs to be carefully detailed.
A metal plate tying the two walls together is an important detail. Alternately, extend the dbl. top plates over the beam, lowering the beam 3" so the plates can still lap in a conventional manner. If you go with a hardware hanger or a ledger, the beam should be strapped to the sidewall top plate to hold it to the main structure in a wind storm or possibly an earthquake.
Along wind storm lines, be sure the beam is well connected to the outer post, and the post tied into the foundation, as there can be significant uplift forces on an open porch roof.
I wouldn't be taking you father-in-laws key from him or you'll find yourself outside sleeping with the dog.
I think I understand all your dimensions and explanations. Very good...except I want to clarify two things: A.) The 260" long beam runs PARALLEL to the 160" long beam, but they are NOT side by side. That is to say, they're separated by 10' or so, and B.) When you say the 330" and 264" long joists are PARALLEL, you mean PERPENDICULAR.
If so to BOTH those issues, then the following applies and you can still let you father-in-law help with the remodel.
1) These are older style glue-laminated beams. (Beams now are 5 1/8" wide.) These beams are fairly "beefy" which indicate they are holding up a significant part of your house. In fact, they are size appropriately to hold up 2 stories.
2) With the holes, their size has essentially been reduced to 5 1/4" wide x 10 1/2" high. (I'm guessing all the holes are drilled up from the bottom about the same distance.)
3) The maximum load on the beams, (this means when all your friends come over for your daughter's birthday party and stand on the beam,) is about 1,000 lbs. per foot.
4) The 60" beam will support a gazillion pounds plus a car. No worry.
5) The 160" long beam will barely support 950 lbs. per foot, depending on the sources of wood, etc. (I don't know where this is located...I doubt Kenya.) However, the good news is that is a lot of support and I wouldn't worry about being 50 lbs. off the MAXIMUM allowable load for that beam.
6) The 260" long beam has some problems. We calculate beams for bending, shear and deflection. This beam can support about 350 lbs. per foot, about 600 lbs. per foot and about 250 lbs. per foot. Not so good.
Now, the good news: beams fail by cracking over time or bend and allow walls setting on / near the beam to settle and crack. So, we can monitor the area over this beam and see if cracks develop in the walls above the beam or the beam starts to crack. (You probably won't see the beam start to crack, because this failure is going to be "horizontal shear". Which means cracks will be horizontal in the beam and be disguised by the grain.) But you will see cracks in the walls above the beams until they become unsightly. Beams are designed to fail in tension first...not in compression, which would fail with an explosion...that's the good news.
Houses are grossly over designed (here in the states). Depending on where the hole is drilled (how far in from the end of the beam) it may not matter...much. If you want, let me know 1) where the hole is located along the beam, 2) species of beam, (or if you don't know let me know where the house is located,) and 3) keep all waterbeds and parties over 100 off this beam.
Best Answer
Yes it is ok to add your wall and box in the vent lines. This is is very common, in fact.