Is there a max limit on how much can I contribute to 529 plans ?
Can I assign to multiple beneficiaries ? Will it affect their scholarship or student loans ?
What will trigger a gift tax ?
No. You will not be able to assign multiple beneficiaries to a 529 plan. However, what you can do is setup multiple 529 plans for your children. For example, if one child has leftover funds from their 529 plan, you will be able to rollover those funds into their siblings separate plan.
Generally speaking there is no limit on how much you can contribute to a 529 plan. But, if you contribute over the annual gift exclusion amount then that would require you to file a gift tax return. A single individual, could potentially give up to $14,000 ($28,000 if each spouse contributes $14,000 separately to the plan) without any gift tax issues.
Please click this link for more information on how it affects financial aid
Also here is the IRS – 529 Plans: Questions and Answers as a reference