You are lucky, Ben is nearly one and keeps pushing his morning sleep to 1pm today, he was happy as though so thats ok!, yesterday he was grizling at 10am though and needed a sleep, so everyday is different!!
Playgroups alwasy start at funny sleep times aye!!,
I'd say just give it a go, I take Ben to different playgroups and if he gets cranky we just go, I have friends who keep there bubbas at home as they must sleep between 9 and 11 in their cots etc but I think thats kind of sad as they are missing out and he loves his music group etc and just crashes in the car/pram on the way home or a has a sleep in the arvo. Relax on the routines I say
Have fun at playgroup, Lucy will have a huge sleep after them I'm sure !!