How about splitting your snowball into halves or even thirds?

I would definitely up the retirement to 15% by doing 401k with whatever the company will match and since you are so close to retirement consider doing regular IRA for the tax deduction. Do this until you have an amount in the retirement you are comfortable with. Speaking from personal experience you never know how soon you will find yourself forced into retirement. We certainly hadn’t planned on taking dh’s ss at age 62, but we ended up having to, paying it back and now it’s all a mess.
The kids need to be doing their part to get ready for those college bills, my kids both worked and it didn’t hurt them at all. Set a cap on how much you personally will put back. Maybe offer to match what they put back up to a certain amount.
If you did thirds you could put the rest on the Sallie Mae. Then after you hit your cap on the other two throw it all at Sallie—she’s such a biddy and I truly celebrated our divorce from her!