You're nuts to borrow money from your parents to start a business.
Now if your parents are very well off, and thinking of the loan as more of a gift, then I'd say go ahead. Anytime you borrow money from, or loan it to, family or good friends, then think of it as gift. If your parents can't afford it to be a gift, come up with a new plan.
I would say most of the successful tree companies I know about, were started from scratch, profits re-invested, and credit slowly built. By slowly building a company, you learn how do deal with the operation's scale at a slowly increasing pace.
You already have a stump grinding business, so you have saws, trucks, and other tools. You climb, so I assume you have basic climbing and rigging gear. All you really need at this point is a chipper and chip truck, maybe just a chip box on an existing truck. I've worked for start up companies that chipped into non-dumping, home made, plywood boxes. After a few weeks of that, you'll end up using the profits for an old, used, 5 ton dump, then in time a newer dump.
I've also run old used chippers, they get the job done and can be had for a couple, two, three thousand dollars. They can also be updated as the profits roll in.
A lot of tree companies don't own bucket trucks. If you need one, rent it. If there's not enough profit in a job to cover rental, bid the bucket work higher.