I cannot comment on bugs, but we did run Lodore at 4,500 earlier this year. 4,500 is nowhere near bank-full for Lodore; it's only "high" because of the dam upriver and we don't see it a whole lot. The rapids are less rocky, a little more pushy, and the waves a bit bigger. Overall, I think it's easier than at 2,000, so if you'd have brought the kids at lower flows, then they should be good to go at this level too. Scroll up in this thread to see a video of a raft and a kayak run HHM at 4,500 earlier this year.
Have a great trip!
"A witty saying proves nothing."
- Voltaire (1694-1778)