Kara yes Finn was on 1 nap at 12 mths for daycare, we had no choice as they only nap them once per day.
At 9 mths we flew to UK and he really slept very well there, naps and all. When we came back and got over jet lag, by 9.5 mths he was refusing his PM nap. And it was like one day he was taking it and then a switch flipped and he just refused. I was LOSING my mind, I had a long thread on Naps and Stacy basically said 'he's telling you he won't transition that way'. So we had to do short AM long PM. It had kinks and I started with 50 mins, then 40 mins (I think) then 30 mins then he got OT so back up to 45 mins. Soon we just moved to 20 mins because he was still not going down easily. So around 11ish months we did the above schedule then over 4 weeks we just moved out that A time and one day I just didn't offer the morning nap. Finn was not a tweaker he needed big overhaul changes to really make a difference.
I'll dig up the thread, it's always worth looking back on it hehe
When you have 2 and have to get out DC2 has to be more flexible, without choice. There's not much you can do but to deal with those nap days as they happen. When you can be home then I would try a shorter AM and your A time is likely going to be around 3-3.5 hrs depending on nap length. I would error on the side of caution with A times, better to have two short naps than only one and a heck of a long time to bedtime!
(((hugs)))