GTV to ilr as a main applicants and dependents' extension?

My current GTV status is valid from July 2024 to July 2026. I plan to apply for ILR in June 2025, one month before completing 3 years on my GTV (which started in August 2022). I have questions about my dependents:

  1. Am I required to extend my dependents’ visas when I apply for ILR, given that their visas remain valid until July 2026, regardless of my ILR application? If my wife will have been a GTV dependent for 3 years with 1 year remaining on her visa (expiring July 2026), is there any refund available for the remaining year of her IHS fee?

  2. Should I also apply for a 3-year extension for my son’s GTV (currently valid from July 2024 to July 2026)? If I also need to extend my son’s GTV when I apply for ilr regardless remaining period of my son’s GTV-dependent visa, would it be “wasting” money on 3 years of GTV-dependent fees and IHS charges, as I understand that once my ILR is approved, we can immediately apply for British citizenship for my UK-born son (as per Apply for citizenship if you were born in the UK: If you're under 18 - GOV.UK).

Thank you for your assistance!