British child, Illegal Parents

Hi Guys, I'm seeking some help and advice. My partner and I have overstayed our visa over 13years ago. We have a 12 year old who is now a british passport holder and a 6 months old baby. we have recently applied for Zambrano residency and is awaiting a response.
My question is - I am hoping to apply under FLR O and was wondering if anyone could give some advice as to the best way to go about it, and if anyone could shed some realistic light on my chances I would really appreciate it. Solicitors at time give false hope and I have grown so tired of throwing money at this situation to no avail. Please help.

One of you will qualify for FLR(FP) under the parent route, but the fee is going up with the Surcharge of £600. That will be costly.

I believe Zambrano should succeed, but it will not lead to Permanent Residence, but FLR (FP) will lead to ILR .

Obie wrote:One of you will qualify for FLR(FP) under the parent route, but the fee is going up with the Surcharge of £600. That will be costly.

I believe Zambrano should succeed, but it will not lead to Permanent Residence, but FLR (FP) will lead to ILR .

Hi Obie, thank you so for for your prompt response, I'm aware of the FLR(FP) under the parent route, but was concern that one of us might be left behind in the illegal situation. So far come to realise that the only way to apply as a couple would be FLR(O) and was wondering about the success rate of these type of application.
Also if one was to go down the FLR(LP) route is there any way of the other regularising themselves???
Also could you expound on the £600 surcharge, I'm not familiar with it.

Thanks in advance x