Well the answer given by 404 to the kids' ages question ie 9,2 and 2 is the only correct answer and the key lies in the number of trees statement. Product of ages was 36, sum of ages = to number of trees. Now takes all the possible combinations of ages and (sum= no. of trees) 1,6,6(13) 2,2,9(13) 3,4,4(11) 1,1,36(38) 1,4,9(14) 1,2,18(21) 1,3,12(16)
2,3,6(11). 2 possible combinations gave the same result when summed up. These are 1+6+6=13 and 9+2+2=13 so there was still a degree of ambiguity which was resolved when the friend mentioned "oldest". From the above it is clear that 2,2, and 9 is the only possible combination which satisfies all the conditions.