Two easy but fun hikes in central NJ:
Plainsboro Preserve https://www.alltrails.com/trail/us/new-jersey/plainsboro-preserve
Sourland Mountain Preserve https://www.njhiking.com/sourland-mountain/
Check out AllTrails for suggestions. You can sort by mileage and difficulty.
Personally I'm wary of giving away hiking locations online since I've seen too many of my favorite spots get overrun this spring.
Harriman just over the border, start from the Elk Pen. Lots of trails to stitch together, here's one loop.
https://www.alltrails.com/trail/us/new-york/elk-pen-loop-trail
Can do the long version of the peanut loop on the Palisades
Probably closer to a half days, but there's a fairly extensive trail network at Hartsthorne Woods, Shark River Park, Wells Mills and Allaire.
Wharton! It's mostly flat, and has some amazing trails through the Pine Barrens. You can see the fire lines from past forest fires. There is a nice bit of water, as the Mullica River weaves through. Ticks and mosquitos are less terrible than other places (in my casual observation), but still wear Ultrathon or some other product with deet. It's awesome year round.
Pretty wild hike I went on recently where there was hardly anyone else was the Four Birds Trail right off RT 23 in Newfoundland. It's a 5-6 mile trail (6 if you go out and back, 5 if you make it a loop by walking the last two miles on the road).
It's steep at times and a nice ridge hike with at least two great overlooks. It's really in the woods far away from much of anything and, like I said, hardly anyone there the entire time I was there. Here's a link to the AllTrails: https://www.alltrails.com/trail/us/new-jersey/four-birds-trail--2
I've hiked this in total both ways three times, though only once as a single throughhike.
Strongly advise getting Guthook's app,
http://www.guthookhikes.com/2013/03/guthooks-guide-to-appalachian-trail.html
https://play.google.com/store/apps/details?id=com.highsierraattitude.atcomplete
And the AT guide by AWOL, rip it apart to just carry the section you need, the chosen binding is made to be separated to save weight.
Bear canister is required imho since you're new to this.
Merrell Moab 2 are my go to.
It's a fight against elevation, get your legs in shape. It's a relatively simple hike once you break it down to four separate days of hiking. And you can stop in and get pizza, McDonald's, italian subs and ice cream on route, Heaven Hill Farm ice cream and lunch being the highlight for me. Annabels Pizza also really good.
Learn how to bear proof your campsite, those 72 miles have the highest or second highest density of black bears along the entirety of the AT. (Pisgah in NC might have more now).
There are several Meetup groups that backpack the AT in the area if you want to connect with people who have experience and can offer up tips.
South Mountain around the waterfall is PACKED on weekends in these covid times (unless the weather is crap), tons of families and kids. Whatever you do do not try to park in the little lot thats close to the falls, it's a nightmare. If you DO go there, here's what I recommend:https://www.alltrails.com/explore/map/tue-27-oct-2020-13-57-967990d?u=i
You park in crescent loop all the way around past dog park, then walk down red trail until it turns to the wide gravel trail, then cut over on red/white. This takes you to a small path by the stream that leads to hemlock falls. It's a very rocky area of the stream and there's lots of nice little falls and bore holes. Less crowded than the falls area, probably a better "we're on a date and I know this cool spot" vibe, and if you want you can walk the extra bit down to hemlock falls too.
If you could drive an hour your options would get a lot better -- Norvin Green is good as someone else suggested. The other parks I would suggest are also around an hour: Schooley's Mountain Park and Hacklebarney State Park are both great ones for novice hikers and have waterfalls.
If it wasn't so far into fall I'd suggest some of the more weird NJ ecology hikes like Great Swamp or Cheesequake, but I don't think they're really good to do this late in the year.
I would suggest Vista Loop at Ramapo Reservation in Mahwah. Can cut it short if needed for new hiker. Good views and a little less of a drive.
> Note: Campsites are closed until further notice for backpacking. Please check with the Byrne and Wharton State Forest for more details.
The Pinnacle and The Pulpit is my favorite day hike within a two hour drive of Philadelphia.
Time of day! Sunset is after 8pm right now, go on hikes 5:30/6pm, crowds are lower most places, more animals, cooler. Could also do very early I guess, but I'm not a morning person.
I just did this short one near stonetown, hard climb but great views and only saw one other group:
https://www.alltrails.com/trail/us/new-jersey/windbeam-mountain-overlook-trail
All trails also has a search where you can turn on a filter for "lightly trafficked", which isn't always accurate, but it does help.
It's fairly rugged; AllTrails ranks it as moderate. There are a couple of the trails that are easier, but without knowing your kid I can't say for sure. My 20 lb dog does fine on them if that means anything to you.
This one is labeled as kid-friendly. Check out this trail on AllTrails. https://www.alltrails.com/trail/us/new-jersey/white-square-loop
Thanks for all the responses. I got the Garmin Forerunner 645 for $220 on amazon https://www.amazon.com/dp/B07DPMQ59K/ref=twister_B07DR9TK2Y?_encoding=UTF8&th=1