The moment you buy DLR.TO, you have in effect exchanged your money. So the fx risk is mostly about holding USD cash for a week.
One issue is that you wouldn't want to hold cash in your portfolio. So rather than DLR.TO, it may make sense to use another equity which is listed in USD and CAD, and which you have a large allocation for in your portfolio anyway. This way you can adjust the USD and CAD portion of that equity, so that when you want to rebalance, you can sell or buy the cad or usd shares.
This could be done with many equities that trade in USD and CAD, like banks.
I've recently come across another Horizons product, a mid-term us treasury bond etf that can be bought in cad and usd (HTB, HTB.U). It would be worth investigating whether Questrade can marshall those over. It also uses some technique to try to reduce the amount of income vs capital gains, for tax efficiency in non-registered accounts. One could allocate, say, 4% shifting the allocation up and down between usd/cad as the rebalancing requires either currency.