@GrandOldDuchess
School trips
Nurseries, childminders, schools and colleges will not go on educational visits at this time. This advice will be kept under review.
That's the guidance, as updated yesterday.
So yes they've broken the rules.
But I think that given you're alright with some rule breaking, eg the park, it's difficult to then expect them to know you're not OK with this rule breaking.
I, personally, would have had an issue with the park and would have raised it. You didn't. And though you state you've been careful with the risks etc, you surely accept the the biggest risk full stop is nursery attendance...
Raise it. Have your child excluded, but there will obviously be fall out in that she misses out or the sctivities don't then go ahead (they shouldn't be anyway, but your raising it will have been the reason!) You could rightly raise it with ofsted.