That would be perfect if they both are able to stay in the home, and don't need the money for health care (which is the OP's concern). The worst case, both financially and personally, would be if one died, then the survivor had to sell, but was only able to take the $250K deduction.
I found this exception from Nolo: "If your spouse dies and you subsequently sell your home, you qualify for the $500,000 exclusion if the sale occurs within two years after the date of death and the other requirements discussed above were met immediately before the date of death."
Link to the full text is here:
https://www.nolo.com/legal-encyclopedia/the-250000500000-home-sale-tax-exclusion.html
IF it appears that only one parent might need $ for health care costs, and the other parent wants to stay in the house, then a HELOC or a reverse mortgage might be acceptable. But see the many warnings about what must go right if your choose the reverse mortgage path (primarily, paying property taxes and insurance, and never letting them lapse, and responding to all bank inquiries).