I certainly wouldn't criminalise them, no. I think it is extremely unlikely that a 10 year old can understand the possible consequences of having sex, but when people get to 12, 13, 14 etc then for me that's a different scenario. No-one should be pressurised into having sex, that is assault, but consenting sex between people of a similar age and 12 and 15 is similar enough for me is not something which ought to be punished. In Germany the age of consent is 14 and it's fine if your partner is anything up to 4 or 5 years older than you, no-one bats an eyelid, and there is a far lower teenage pregnancy rate there than here. You can't just criminalise things you personally feel uncomfortable with.