The gloweth development is a bit out of town, but would be well placed for 3milestone school there is a good play group in the church there and also stay and play at the school.
Tregolls would firmly put you in catchment for that school. It is also longer to walk to town than you would think.
Perranporth - well you either love it or hate it. Dead in winter, teaming with tourists in summer. School and preschool v good but not much going on in the town.
Kenwyn is lovely but don't discount the opposite side of town, especially around Redannick park. Always good rentals and the park doesn't look like much but is a real local hub. Lots of young families and while you would be in Bosvigo catchment lots of families there use the other Truro schools and you are the right side of town to get out to kea and Chacewater schools.
The pottery preschool is excellent and this is the place for fantastic baby and toddler groups. In the baptist church and very friendly. The ladies that run both are lovely.
Lots going on in Truro for preschoolers, it really is a lovely place to raise a family. I thought that when mine were tiny, even more so now they are older.
Good luck with your move -- any more questions? HTH!