Depending on their expenses, your mother might be able to retire now.
What the heck are they doing with half of a gutted house? That's the big question! Including their own home, they've got 51% of their worth in real estate. Are they flipping it? Renting it? Is it a vacation home shared with the other owners?
You don't mention if the cash is earning any interest. If it's not, something should be done with it. Leave 6 months of expenses in checking, and $25,000 goes to paying off the HELOC. The rest either goes toward the gutted Jersey Shore house, or into a CD ladder, and/or is partially reallocated.
To get to a 50/50 stock-bond split of their current investments, they'd need to trade $47,500 from bonds for stocks. Or, if you count the bonds and cash as the same asset class, then, after the $25,000 HELOC is paid, $130,000 would get them to a 50/50 split. It just depends on what amount they're comfortable seeing in stocks, and I would suggest re-balancing gradually, a little every month, over the course of the next two years, after which they'll receive SS and feel more secure.
They/you can switch over anything that's already in stocks to VTSAX without feeling nervous about it, since it's just trading stocks for stocks, and you're probably getting them more diversity at a lower cost. Find out how your father's IRA is invested.