2.5? Wow, that's a wide tire! My widest are 2.35, and that's on the no-suspension bike.
IMO, the answer to your question is "maybe". Whenever possible, I like to use the right sized tube for the job. However, the widest tubes that I can get for my 29er are 2.1, and I use them with 2.35 tires with no issues. Then again, I'm running at very low pressures.
If it were me, I think I'd buy/beg/borrow a couple of wider tubes just for the peace of mind while riding solo.