Arguing that people under 29, particularly kids don't need to be vaccinated.

They can pass it on to the vulnerable. "a growing body of evidence suggests that COVID-19 vaccines also reduce asymptomatic infection and transmission" https://www.cdc.gov/coronavirus/2019-ncov/science/science-briefs/fully-vaccinated-people.html

No death and the possibility of getting natural immunity

They die. Over four and a half thousand people under the age of 29 in the US have died of covid. https://www.cdc.gov/nchs/nvss/vsrr/covid_weekly/index.htm In canada there have been 95 "29 and under" deaths attributed to the virus as of Oct 29, 2021 https://health-infobase.canada.ca/covid-19/epidemiological-summary-covid-19-cases.html Figure 7.

they haven't been vaccinating children

Wrong. The results of the clinical trials on children are in, so yes they have been vaccinating children. "Since the summer of 2021, thousands of children across the country between the ages of 6 months and 11 years have received the Pfizer-BioNTech and Moderna mRNA vaccines to collect data on their safety and effectiveness." https://covid19.nih.gov/news-and-stories/ensuring-vaccine-safety-children

the FDA admits that the impact on kids is unknown

Says only you, so far. Maybe you have a link.

resistance that will diminish over a matter of a few months

But not by a lot. "Both vaccines lose some effectiveness but are very good at protecting against hospitalization." "Some people are currently advised to get booster shots, but experts say overall the vaccines are still very effective." https://www.healthline.com/health-news/what-we-know-about-how-long-the-pfizer-and-moderna-covid-19-vaccines-work

Vaccinated people spread the virus for a shorter period of time. "Vaccinated people are less likely to spread Covid, new research finds" https://www.nbcnews.com/health/health-news/vaccinated-people-are-less-likely-spread-covid-new-research-finds-n1280583