Using E-Certificate with 2 pax itinerary
 

Maybe I just have not tried to do this before...but I am sure that I have.

I am trying to book a flight with 2 pax..using an e-cert.
It will not let me do it. I get: "this promotion is not valid for that number of people".
Is this normal? Anyway around it. Booking separately is a problem due to E+ access for the other person.

You just need to call in and have your companion moved up to E+, I do it all the time. Most ecerts only allow one PAX.

The number of passengers allowed per e-certificate discount will depend on the T&Cs of that particular e-certificate.

That's not the issue. He's not trying to apply the e-cert discount to both pax, rather he wants to have both pax on the same PNR while applying the e-cert to just one.

This is often possible on other airline sites with their certs, but UA does not have this capability on their website.

That is exactly right. Not trying to "double" the value of the e-cert, simply want to get both pax on the same PNR.
The reason is obvious. The other pax is a child and would be on her own on a separate PNR. It was suggested above that I could just call and have her moved up to E+.......but we know that it is very likely that a sweep at some point could move her back on her own to E+. Linking the two in the remarks probably would not help as the sweeps appear to be done by computer.

I also will be using CR1s to upgrade....but the non elite child would not be linked to a 1K for any priority.

Is there upgrade space in F right now? If so just buy and upgrade the kid first.

If you are going to sit in E+ just keep an eye on the seats, How far out is your flight, I have only seen people swept out recently due to equipment change.

I would say "possible" more than "very likely". You have to choose - discount, or peace of mind. Personally, I wouldn't worry about the sweep issue - you can always call back to get her moved back.

People are never "linked" for upgrade priority. Before the DM, status only determines which waitlist you get on (at least the way FT understands it), and that's based on the sponsor's status, not the recipient's. And once on the DM list, everybody's on their own regardless of whether they're on the same PNR or not.

Child on his own PNR?
 

I would like to redeem some E certificates and understand that each person needs to be booked on a separate PNR in order to use the E certs. I have no issues doing this with my Wife as she's been on a separate PNR many times when I've been travelling on business and she comes with me. However, would there be an issue with my 2 year old child travelling on a separate PNR with us (same flights and adjacent seats)?

We would essentially have 3 passengers (me, wife, and child) on 3 separate PNRs, so we could use 3 E certificates. Just want to make sure that there won't be any issues with the child on his own PNR.

The last time I used 2 e-certs for 2 people I followed SOP by calling web support and when all was said and done we were on the same PNR. I thought this was not supposed to be able to happen, but it did.

Just call and be transferred to Web support. They'll book it over the phone and apply the certificate. I do this all the time. You just need to have patience with the person you get on the phone... they might not immediately know what you're trying to do.

I sponsor lots of E+ upgrades. Very very seldom see any sweep kick the other folks out. Just make sure they are seated next to you, as I've been told this helps (though I'm not necessarily sure how.)

The sweep occurs if you clear upgrade into F, then your sponsored E+ will be swept back into E-. You have to be in E+ in order for others to be in E+.

The OP has not indicated that an upgrade to F is in the works. Hence, I don't see how this relevant.