We had that provision last year 100% 1:1 (nursery used own staff) + SALT (half termly to termly visit) + autism outreach (was supposed to be weekly TA visit and half termly to termly visit by autism teacher but we only had about 5 visits in a year).
It was not enough.
It depends on whether this will meet need. DS has a list of issues that come with his ASD as long as your arm - severe speech delay, high level of stimming, some minor self injury, tantrumming, intolerance of other children playing near him / with his things etc etc. The nursery staff did not know how to engage him in play or tasks. They got very little support and training as the outreach service never turned up and if they did they gave 'advice' but never set any programmes or demonstrated any strategies.
If its not in a statement then there is no guarantee eg the 1:1 won't be used for other children, or the autism outreach will come as often as they said, or that SALT will happen.
I would appeal for a statement. You can pull out of an appeal at any time - but by the time you got to tribunal (6 months) you would know if the provision was sufficient or not. Whereas if you do not appeal and you put your trust in it working and it doesn't you will be starting from scratch.
What specialist provision are you asking for that is going to panel?
My personal view - and it is my view based on my child who has moderate autism (not mild) and severe speech issues is that very very few mainstream staff have enough experience of autism to deliver autism strategies. It could work with alot of training and support (very frequent visits from outside professionals) with a child with lesser needs. Mainstream teachers have maybe one day training in autism every few years. Nursery staff don't get any training. Its a very low level of knowledge - the nursery are not going to become autism experts overnight.
You must get clear information on how often other services are going to come and what they are going to do to support the nursery.
Also if is going to need a statement in future it needs to be in place BEFORE school so that a smooth transition into school can be organised.
Age has nothing to do it with by the way - its whether the needs are met. My DS got his statement at 3.3 and we improved it at tribunal when he was 3.11. But he should have got his statement at 2.5 as there was no new evidence really his needs were obvious at 2.5 and it was equally obvious that an untrained 1:1 would never be able to meet them.
However it also depends on what you are asking for because if you are not looking for anything extra eg specialist placement / more SALT / OT etc then you will have nothing to appeal against. You need to be asking for more than you have.