I don't think it's a risk at all. The only potentially good NBA player we'd lose in those two trades is Collins.
Plus, the savings. Crabbe will be tradeable next season.
There's 3 good scenarios that could play out in the summer of 2018.
From the best possible (and unrealistic) scenario to the least best (assuming Nurk has a cap hold and is waiting to be resigned)
1.) Melo and Wade like playing here together. We trade Crabbe and Aminu so that Lillard, McCollum, Nurkic, Vonleh, and Swanigan are making $60M-ish. After a very competitive season, Melo and Wade are willing to resign for cheap, $7M contracts. That leaves around $30M in cap space. Lebron is a free agent, and looking at a group of Lillard, McCollum, Nurkic, and his buddies in Wade and Carmelo, Lebron decides to sign with Portland, giving us this:
Lillard / McCollum
McCollum / Wade
Lebron / Carmelo
Vonleh / Swanigan
Nurkic / Vet FA.
2.) Melo and Wade resigns for $15M a piece, putting us over the salary cap. We then make a sign-and-trade for a big time free agent (Crabbe, Aminu, and a pick), or trade Crabbe, Aminu, Swanigan, and future 1sts for a legit all-star.
3.) Melo and Wade leave, we resign Nurkic and sign cheap veteran pieces to replace Wade and Melo on 1 year deals. We'd have our sights set the summer of 2019, and using Crabbe's expiring deal along with pieces like Vonleh, Biggie, and future picks to trade (S&T) for an all-star.
Basically, I don't think you can go wrong by adding more talent, especially house-hold names, to a small-market team while also creating future flexibility and more options for building a contender down the road.