Is it in your contract? Do they pay for vacation days (to hold the spot)?

If it's in your contract that you take 5 weeks, then they can just deal with it. I'm sure you were upfront about it in the interview. Any other profession would have at least that much time off after 28 years, why not you? If they really start to give you grief, remind them of that.

I wouldn't be comfortable charging parents for more than 3 weeks vacation, so I would probably just increase monthly fees to accommodate, and then not 'charge' for vacation days over and above. Just my personal preference. That way parents feel a bit better about not having to pay all 5 weeks (even though they really are).