I don't have twins, but have 2 children, ages 29 months and 6 years old. They still nap.
I don't believe that at this age, or through 5 years old, that naps are 'completely' 'gone.' But it changes and evolves. And a child will still nap, if given the opportunity and if you cue into their needs.
That being said. If your kids are not doing their morning nap, early...then simply move it up about an hour or so. It's not hard.
And yes, keep flexible enough for the other baby who still seems to need his morning nap or both.
The KEY... it to 'CUE' into your children... and observe them closely. A child this age will STILL get tired and need a nap.
My son, has taken 2 naps a day, since he was a baby. Sometimes he doesn't need his morning nap. Sometimes he does. But, he WILL take his afternoon nap, regardless. I know this, because I know him and his 'cues.' No matter what... even if his naps are now an hour later... I KEEP TO THE SAME pre-nap routines. No fail. My son knows it like auto-pilot, and it is not a struggle to put him to nap. It takes me about 1/2 hour for 'wind-down' time, prior to nap. Then he naps... putting him down in the crib when he is still awake. He falls asleep on his own.
My daughter, will still nap in the afternoon, after school. She does this about 2-3 times a week. If not, we have a 'quiet-time.' My kids know it like the back of their hand. So, it's not a struggle.
The KEY here... being CONSISTENT AND SAME ROUTINE, EVERYDAY. I have done this with my kids since they were babies. So, it's no shock to them, and it's just a part of their day, and they know it. I don't force naps on them... but I know they are tired and they nap. My kids will even tell me sometimes that they want to nap... they know themselves, by now.
It's just important to keep in mind... that a baby/child fluxes... there will be times (due to developmental changes) that they go through 'phases' of "seeming" to 'not' need a nap... but if you keep to a 'routine'... and still put them down at about the same times... you will keep 'them' consistent and build up good nap/sleep 'habits' in the LONG term. If they don't nap, then fine. Take them out and don't have one that day... but the next day, just keep to your routine. The same thing.
So, it requires the parent to be flexible, to know their baby's cues, and know that they are tired... it is not a finality.... that napping will disappear entirely & for the rest of their childhood. Especially at this age and older. In preschool and Kindergarten, kids still nap. They need it.
So, gauge your children. I believe, that at this age, your babies are just changing and going through developmental phases. It's normal. It is not just a cut and dry thing...that you 'have to' get rid of their naps. No, not at all. Just adjust it. KNOW that naps ebb and flow.... but are still needed. It is an important for their development too.
For example, for me, I 'schedule' my kids naps, according to my daughter's school end time and when I have to leave the house to pick her up, then come home, and what not. So, my son naps at about 10-10:30 a.m. For 2 hours. Then, after I pick my daughter up from school, they both nap at about 3:00-3:30. For 2 hours. Then, they go to bed at night at about 8:00-8:30. And they sleep fine. Their afternoon nap does not interfere with their night time bedtime. My son has a pattern, and I know it and when he gets tired. He's like a clock.
For you, you can still put one twin down for his morning nap since he still seems to need one. Or try putting both down, still in the morning. Or, you schedule it for around 11:00 as you said. And see how that goes. Main thing is to keep CONSISTENT. A baby/child will get attuned to it.... and it's better than having an 'over-tired' baby. My kids, because they nap, are rarely fussy, and they are energized by their naps. It keeps them even keeled.
The transition in changing nap times are not 'hard.' If you must make the naps later, just try in 1/2 hour increments. And see which one helps. But I would not forgo naps 'completely.' They will still need to nap and will naturally get tired.... thus, CUE into your babies... and gauge them. Sometimes they will only need 1 nap... on other days, you will find that they will still need 2 naps. It can vary. So, observe them. That is the best. It worked for me all these years and my kids still nap. Willingly. :)
Like Laura S., my nap/bedtime schedule with my kids is the same all the time... the same 'routine.' It REALLY helps in the long run...
Good luck,
Susan