I come across many people entering their 50s without much retirement savings. They will have to either work substantially longer than they want or substantially lower their lifestyle in retirement. Neither is a good option.
If your child has a job this summer, help them create good financial habits so they do not end up in this situation when they are 50. Suggest they save 15% of what they earn for retirement. If you want to help them and give them a feel for how employer sponsored plans (like 401ks) work, tell them you will match their contributions dollar for dollar up to 15% of what they earn. That provides additional encouragement to make saving for retirement a life-long habit.
A Roth IRA account is a great savings vehicle at this age. Contributions are made after tax and withdrawals are tax free after they reach 59.5 years of age. Have them buy a total US stock market mutual fund or exchange traded fund and leave the money alone for the long-term.
It is not that the amount of money they are saving that will make their retirement. The important part is teaching them the habit of saving 15% of their earnings for retirement. If they do that throughout their career, they should be in financial position for a comfortable retirement when they reach retirement age.
While you are at it, encourage them to give some of their earnings to a not for profit that would be of interest to them. 10% is a good target for this type of giving.
Have a great summer.