Also, how do Goten and Trunks compare with them in terms of their power. I'm guessing they are stronger since they can turn Super Saiyan at a younger age. Is Goten stronger than Trunks because he is the son of Goku?
I think it would be convenient and fair to compare the power levels of their characters when they are lesser than 13 years old, considering Goten and Trunks's age.
- You are wrong about Goten and Trunks being the strongest. The strongest of the bunch if Gohan. Gohan according to the manga is 9 years old during the Cell Games and 11 according to the anime. He attained Super Saiyan 2 at this age and was also stronger than Goku and Vegeta in his Super Saiyan form even at that time hence obviously stronger than Kid Vegeta and Kid Goku and also Kid Goten and Trunks, considering the fact that they haven't mastered Super Saiyan 2 yet.
- You are wrong about Goten being stronger than Trunks. Kid Trunks is a year older and has more fighting experience. He trained with Vegeta during his childhood while Goten trained with Chichi and only began training with Gohan really late. Also, Goku himself stated that Trunks was stronger, when they were being taught the fusion dance by Goku, which you can look at here.
- Ironically, the strongest fighter in the multiverse, was the weakest of the bunch in his childhood. Kid Goku was significantly weaker than Kid Vegeta. In the Raditz saga, Goku was 25 years old and even along with Picollo, struggled to defeat Raditz. Kid Goku is obviously significantly weaker than this Goku. Raditz was also stated to be equal in strength to Vegeta's and Nappa's Saibamen. Kid Vegeta is shown here easily destroying Saibamen like they are nothing, making him stronger than Kid Goku.