Visa type for ILR dependent

Hi,

I have received my ILR in Dec 2019. My wife & 2 sons (under 18 years) joined me in UK in May 2015. My wife was on Tier 2 ICT from May 2015 to Nov 2016 & kids were on her dependent visa. In Nov 2016, my wife changed to Tier 2 dependent visa (as my dependent). Now my wife & kids visa is due to expire in April 2020. I understand that since my wife & kids visa status changed in Nov 2016, their 5 year counter for ILR starts from Nov 2016 & they are not eligible for ILR until Nov 2021. As their visas are expiring in 2 months, what type of visa extension should my wife & kids be applying for?

Apply for a tier 2 dependent visa extension, which will be a 3 year extension.