Need JR pass if have Welcome Suica

Hi! We’re a group of 4 adults and 2 kids (ages 5 and 7). Do we need to buy a JR Pass if we already have a Welcome Suica?

Our itinerary is:

Dec 28–Jan 1: Tokyo
Jan 2–4: Karuizawa (ski trip)
Jan 5–8: Osaka (with day trips to Kyoto, Nara, etc.)
Flying out from Osaka.

We’re planning a couple of day trips from Osaka and maybe one from Tokyo as well. Would it be better to buy individual Shinkansen tickets for each leg, or get a JR Pass even though we’ll be using the Welcome Suica?