Disabled children's team is part of social services, they will be looking perhaps at leisure opportunities or respite (usually in form of direct payments). This is different to the Education Dept of LA - it is the LA SEN Officers who will foam at the mouth at the thought of ABA.
I would meet them and see what it is they are offering. Having a home ABA programme is no different than your child being in FT nursery. You don't have to tell them if you don't want to - they may well pass the info to SEN team.
Their job is to make sure you can manage as a carer and that your child can access activities they will not be looking at education generally.
Things you might consider would be a sitting service so you can go out, they may advise on childcare (which you can just say is not needed), accessing activities (usually few options for under 5's - usually they run holiday clubs for school age children) etc
What we get from disabled children's team is:
3 hours a month free (specially trained) baby sitter so we can have a night out as a couple
12 hours a year sitter so we can do voluntary work / go to meetings
2 hours per week direct payments for someone to look after DS3 (ASD) while we take DS1 and DS2 out (we save this up and use a half day etc so we can do activities DS3 can't tolerate and DS1 and DS2 occasionally get to do 'normal' family things) - DS3 would not be eligible for overnight respite but in any event they would not pay for that until age 7 here.
Some families get a 'short break' which is a leisure activity for the disabled child e.g. 1:1 swim lessons, riding etc
So generally speaking it is more about support for the parents, siblings, leisure than education for the child. Trying to make sure you don't collapse as a carer / divorce / crack up and end up costing them more
A family support worker is not usually a trained social worker so I would expect they may just be signposting you to other things e.g. welfare benefits, support groups etc
If you get DP you can the money for ABA tutors - just call them respite carers - which they are! Its only about £8 per hour though so won't cover the cost
In my experience most LAs don't offer anything for under 5's
I probably would not tell them about ABA if you don't want the SEN officers to know yet. But actually most social workers are in favour of intensive early intervention because if children don't get a good education then it is social care that ends up picking up the bill when they become adults.
Contact a Family has good leaflets about social care you can download.