You'll definitely like having some sort of spring'ed suspension on your minibike... or rather your kids will (not sure if the springs can handle adult weights). I had two of those Baja Doodlebug minibikes a few years back (same as Walmart one linked) with the no suspension. They were pretty jarring riding around the yard.
The stock DB30 (Doodlebug) came with a 2.5hp engine... that was pretty underpowered. It was fine for little kids but even then couldn't take a hill without a running start at it. But it could barely move me around on level ground. I put a jackshaft on one and re-geared it...and it ran more in it's powerband and did much better for the kids. A 3.0hp like yours will be a great match for that mini!
On one of mine, I put a Harbor Freight 6.5hp engine. That mini was adults-only. It was fast and powerful and would zip me up all the hills in my yard with ease. Almost scary... could easily lift the front wheel.
Looking forward to seeing how yours turns out. Kids love them. I've upgraded from mine to a PW-50 and TTR-90 for the boys.
Cheers!