Pretty hard to estimate. We know that King Vegeta was the strongest Saiyan at this time and even without taking into account the dub statement of King Vegeta > 10k ~ Bardock, having him around 11-12k seems like a decent estimate. His son ought to not be far behind, given how I doubt he'd gain too much power between then and puberty when he surpassed his father as a child and never fought anyone noteworthy enough to ever consider his strength unsurpassed by any outside of Freeza' clique prior to facing Goku.
DB Minus states that the total population of Saiyans is only a couple of thousand, so it really depends on your take on combined powers stacking up in Dragon Ball. I have no doubts the total battle power would be a danger in an simultaneous attack, but considering the strongest Saiyan behind the two royals is probably Nappa manga-wise at likely significantly less than his Saiyan Arc power, I see it at best causing Freeza to be injured but not killed. After all, his concerns of the Saiyans' strength in numbers was a distant threat to Freeza at this point, meaning he could likely combat the combined might of the Saiyan Race at their peak.
Anime-wise though, I could see the Saiyans pulling it off due to 10k Bardock and the rest of his crew being elite tier.
If including non-canon stuff, there's also Tullece being referred to as already being a "top rate warrior" at this point and of course 10k Broly, so in a composite movie timeline, they definitely pull this off.
