riding on tern ebike, or bigger bike?

We're riding the trail in mid-June, staying in hotels and carrying our 5-yr old son on the back of our tern ebike. It's the bike my wife rides most days with our son. We intend to take this bike and my gravelish touring bike. We've run into some rail-trails with deeper gravel and are concerned about the tern in these conditions.

The trail appears almost all hard-packed, or limestone but are there any softer areas? Especially prolonged areas (over 3-5 miles)

Thanks!

There were a few soft spots but they would be measured in yards, not miles. One section was undergoing maintenance and was probably hard packed days later. I found the trail easy to ride from end to end other than that long stretch coming out of Deadwood, but that is because it’s uphill, not a surface issue. I rode it in a day and a half. I hired Bill from Black Hills Discovery Tours to drive my truck from Deadwood to Edgemont. It was a little expensive for me as a single rider but less money and time for a couple plus child to take a shuttle back. I’m going to cut/paste my itinerary below followed by my Strava if day one. Don’t miss Purples Pie Place, I went there directly from trail, then motel which was very clean and comfortable. Sage Creek was excellent. Great reviews for Mickelson on Facebook Rails to Trails and Mickelson Trail pages.

South Dakota: Mickelson Trail 109 miles

Wednesday, August 23
Sioux Falls, lunch at Capriotti’s or Jersey Mike’s
Rapid City, stop at Acme Bicycles
Spearfish, stop at Two Wheeler Dealer
Deadwood, stay at Cedar Wood Inn, dinner at Jacob’s Brewhouse

Thursday, August 24
Breakfast at Lou Lou’s Bombdiggity
8 am Meet Bill from Black Hills Discovery Tours at trailhead 605-920-1020
Depart Deadwood for Custer, about 64 miles
Hill City, Stop at Granite Sports shop, if hungry Box Car Eats & Treats
Crazy Horse
Custer, stay at Chalet Motel, dinner Sage Creek Grill or Mt Rushmore Brewing Co,
Dessert from Purple Pie Place, if time allows South Dakota Outdoor Shop 730am-700pm

Friday, August 25
Breakfast from Miners Cup
Ride to Edgemont, about 45 miles
Drive home
https://strava.app.link/mVlHC530wIb