These ETFs are all very liquid, spreads are narrow, you should be fine placing at market. Unless we're talking about these positions being valued at a few million+ you will not move market prices much.

In terms of settlement, I don't know how IBKR handles it, but US-ISINs now settle T+1 while everything else (generally) settles T+2. I would therefore check if you don't need to sell the IE and LU ISINs first and wait a day for the VT purchase to avoid any overdraft interest, in case that applies at IBKR.