Tier 2 dependant extension

Hi all,
Hi all,
I am currently on tier 2 general valid upto aug 2022. My husband and kids are on tier 2 dependant. Kids visa validity 21 july 2020, husbands aug 2022.
Now we have to apply kids extension, we have filled the forms and IHS fees is showing £1000 per child.
Now our issue is that my husband will become the primary applicant in nov 2020 and we will become his dependants, so all IHS fees which we will pay now for the kids 2 years visa extension will be wasted .
Is there a way to obtain only partial extension, for a few months or a year?

Any suggestions??