St. Augustine said in City of God that we'd all be about 33 (same age as Christ) at that time it was thought that unbaptized babies might go to limbo.
Then, again, these words, “Predestinate to be conformed to the image of the Son of God,” may be understood of the inner man. So in another place He says to us, “Be not conformed to this world, but be ye transformed in the renewing of your mind.” In so far, then, as we are transformed so as not to be conformed to the world, we are conformed to the Son of God. It may also be understood thus, that as He was conformed to us by assuming mortality, we shall be conformed to Him by immortality; and this indeed is connected with the resurrection of the body. But if we are also taught in these words what form our bodies shall rise in, as the measure we spoke of before, so also this conformity is to be understood not of size, but of age. Accordingly all shall rise in the stature they either had attained or would have attained had they lived to their prime, although it will be no great disadvantage even if the form of the body be infantine or aged, while no infirmity shall remain in the mind nor in the body itself. So that even if any one contends that every person will rise again in the same bodily form in which he died, we need not spend much labor in disputing with him.
The answer is though, we don't know for sure since no public revelation details heaven.