Goku didn't recruit goten and trunks because they charge at their enemies like an idiot. But isn't Frieza like that as well? Why did Goku recruit Master Roshi who can't even beat Raditz? He can't even scratch the fighters from other universes. Roshi & Tien can be removed and leave space for Gotenks.
Gotenks has a time limit plus we dont know if fused characteres are allowed. Probably not, since fusion would end before the tournament and you would have 11 members in the arena when 10 members are allowed.
Freezer is way much stronger than Gotenks. Gotenks SSJ3 was less strong than duplicate Vegeta in base form https://www.youtube.com/watch?v=L1Jxo4gDdzs . Vegeta and Goku are in a similar level. Freezer is said by Beerus to be in the same level than SSB Goku.
Roshi can beat Raditz by far now. He could handle many Freezer soldiers, he could beat Tien who was able to defeat Burter and Jeice who were over Vegeta's 30000 power level of that time (probably between 40000 - 45000) . Tien could also hold second form Cell, deflect a Majin Buu Gohan absorbed attack, resist a punch in the stomach from mystic Gohan and not pass out, etc. Also Roshi, Krilin and Tien experience are taken into account. In a sparring match, Krilin defeated Gohan by pushing him outside of the arena, outsmarting him. He almost outsmarts Goku in a sparring match too, in spite of being much less weaker than them just like Tien and Roshi are.