Climbing Frame

We are thinking of purchasing an extension kit for our eldest's climbing frame for our youngest's birthday. But getting it early so they get the benefit of it this summer. The thing is we are not sure which one to get. Do we get the one for age three and above which looks very high and will last years, or do we get the lower down one that will be a bit safer but might be boring by the end of the summer and will not enable us to buy the next accessory we would like - a scramble net.