Valuing Future Draft Picks

I was just offered Gronk, Funchess, and Adrian Peterson for my 2019 1st round draft pick in a PPR keeper league. I’m new to future draft pick trading. Not sure how to value them. This is a keeper league. Generally, how should I value future picks? Specifically, what are your thoughts on the trade?

Also, the way our keepers work is we are penalized 1 round from the round we took the player. Ex: I drafted Kareem Hunt in the second round in 2018. In 2019, I’d have to give up a first rounder to keep him. I just talked to the commissioner, and he implicated I would still be able to keep Kareem even if I traded my first rounder, and I would just give up a second rounder.

My current TE is Njoku.
RBs: Gurley, Hunt, Breida, Aaron Jones, and Duke Johnson
WRs: Keenan, Watkins, Goodwin, Keenan Cole, and Mike Williams.

@MikeMeUpp, any thoughts?

No. As a general rule of thumb, don’t give up future 1st round picks in redraft/keeper formats. It cripples you to the core. Funchess and peterson definitely not worth that hassle and gronk isn’t a 1st rounder anyways on his own.

Not to mention I’m more than fine start njoku ROS.