In Ven Bodhi’s translations he renders the term devaputta as “young deva”. I don’t find this adequate; firstly because deva is not a translation. What’s wrong with “god” or “deity” (although the latter is best reserved for devatā)? Moreover, I can‘t see any reason for thinking that devaputtas are young.
In the introduction to Connected Discourses Ven Bodhi admits that there is no hard and fast distinction between devata and devaputta, as sometimes one and the same individual is referred to by both terms. More cogently, in the Devaputta Samyutta we meet, among others, the Sun and Moon, who aren’t “young” by any standard. Other deities are also no spring chickens; for example, we meet the devaputta Ghaṭikāra, who has been in that station since the time of the last Buddha.
In fact, I can’t find any justification in the canon or commentary for why devaputta refers to a young god. The commentary doesn’t distinguish devaputtas as “young”. True, it says they are born “in the lap of the gods”, but this is about the mode of generation, not about their age. It explains how they can be “sons” (and devadhītā are “daughters”) even though they are not born from a womb.
The distinctive features of devaputtas identified by the commentary are, firstly, that devaputtas are male while devadhītās are female. And secondly, that, in contrast with the more generic devatā, they have names (which is true as a generalization). Neither of these have anything to do with their age.
It seems to me that deva vs. devaputta is a distinction in search of a difference. It’s better to translate them both as “god”, with “goddess” for devī and devadhītā.