[ehnto]

Kettlebells can get you a long way for sure, but are not really suitable for the bigger lifts from disciplines like powerlifting and olympic lifting. The biggest kettlebell I can find online is 92kg, even with one in each hand that's not enough for many. Part of the benefit of plates and barbells is you load them up 20/25kg at a timel, two 92kg kettle bells would be cumbersome to get into position!

[polmuz]

That's true. But for parent's objective of keeping their fitness and hopefully their strength, a couple of kettlebells are probably better that mountain biking, and it takes far less equipment and space than a proper rack, bar and plates.