I have mated 2 two old timers before and their babies both turned into ojitchis instead of children. Ojitchis can use the items and they eat tacos for a meal and coffee for snacks.
I'm not 100% sure, but I think that the ojitchis die becuase the matchmaker might not be able to come to them.
You can mate your two old timers if you want but be prepared just incase they do die.
If you wan to you can, but I would because I would want to keep the generation going. And it would stink to have your tamagotchi die and the matchmaker no come, but I think you could still have 2 fall in love the hard way. ^^