I am DMing my first game in a few months and I want to start getting things ready. We are going to be running the D&D Essentials Kit Campaign, Dragon of Icespire Peak and if all goes well, the follow up adventures: Storm Lord's Wrath, Sleeping Dragon's Wake, and Divine Contention.

One of the things that the DM for our current game has done really well that I wish to implement into my own campaign is the inclusion of NPCs from our PC's backstories. He did a kickass job of creating an entire sidequest/bossfight revolving around our Druid's background and I thought it was so cool. Now, as a DM, I'd like to do the same. My only concern is as the title states, How much back story is too much back story. I like the idea of finding ways of tying in the PCs backstory NPCs and making it relevant to the campaign, but don't want to add too much and throw off the flow of the campaign.

Since there will be 4 PCs, I'm thinking of adding 1 PC backstory element into 1 of each module. Basically, 1 for DOIP, 1 for SLW, etc etc.

Any advice is welcome