You should use a 529 college savings account. Read this article.
The drawbacks of an UTMA (custodial) account are two big ones!
1. At age of majority (18 in most states) the money becomes theirs to spend as they please!
2. If the family applies for financial aid for college (FAFSA form) the money in a custodial account weighs 7X more heavily against the family in the aid formula than money in a 529 college savings account.