Aw, Tulip! Glad to know we're helping vicariously!

That's what BW is all about!
First, as you make LOs nap later, you may want to take it a bit slow -- no more than a 30 minute stretch at a time and you may even want to go 15 minutes, depending on temperment. For the class problem, I'd just put him down for nap earlier so that when you wake after 30 minutes it's just in time for leaving for class. I don't know how long it takes you to go to your class, but maybe 10 am nap, wake at 10:30 and then time to get him to class. My bub sort of hates being rushed right out the door so we'd probably either do a 9:45 nap, waking at 10:15 OR if 9:45 is too early, we'd do 10 waking at 10:20. At this age a 20 min nap can be enough to help them make it. If you do a 20 min nap make A time a bit shorter, esp. since you're doing an activity with him -- so maybe only 2.5-3 hours between naps.
Evilmena: It's hard to say why that nap is short. I have a feeling it's the longer A time that's doing it. He may be a bit overstretched, but for our purposes we don't care!

He may start wanting to nap longer in AM, and that's when we cut it short on purpose so that we can get him ready for the 2-1 nap switch. At this age, if they nap too long in AM they'll often skip PM nap which can make him OT by bedtime and give you NWs/EWs etc. (as you probably know!).
Let's just see what happens at moms house before really giving her the business.

If he naps long in the morning and refuses a PM nap, then you can explain to her that too much sleep in the AM makes him unable to rest PM and it's really ruining nights and mornigns for you. But he may limit morning nap on his own. Mine never did -- I always had to wake him up myself. And I protested, just like your mama is, but the BW mods really encouraged me and it made all the difference in the world during our 2-1 switch.