Sorry rainbow for making an assumption about your past dealings with the LA. Yes you probably will get more support and so willthe children, but all being costed to the LA, which makes things worse and worse for LAs
Re children under 10- you say your own are 7 and 10. Most LAs like there to be a 2 year gap between birth children and foster children, though I do have to say that this is not always followed when backs are against walls so to speak. So you would really be thinking of 5 and under, and if you are prepared to take a sibling group, this could be a good offer. However LAs needs are for older children, sibling groups and children with disabilities,
You could talk this over with the IFA and if they agree you are looking at 5 and under, ask them how many children of 2/3 sibs under 5 have they placed
in the last 2 years.
The other thing is that there is pressure by LAs to get children from IFA placements back into LA foster homes as soon as a vacany becomes available, again because of the cost.
The problem for IFAs of course is they know they are only used when there is no LA placement available, which makes it difficult for them to say exactly what is coming their way, but I assume they keep records so it would be quite in order to ask them about nos of children placed. The other thing to bear in mind is with an IFA, a child/ren can be placed from anywhere in the country, miles away from home, just because that is the only placement available, which is very confusing and distressing for the child, whereas with the LA you will be getting a child from your area or a neighbouring authority.
Foster carers are like gold dust- there is an acute shortage on a national basis. So why not have a talk to your LA and as many IFAs as you can. There are usually many IFAs in one locality - they are mushrooming because there is big money to be made!
You certainly should NOT be turned away by the LA or any IFA and to be honest I woud be a bit suspicious of the IFA sw who tried to turn you away with dramatic stores of horrendous teenagers.
Best of luck whichever way you go.