Responding to your question is somewhat difficult because you seem to have several unrelated concerns; dog issues, soil question, disease (primarily virus) and supplier sources. One must also consider how much investment one is willing to make. Obtaining virus free stock can be considerably more expensive than buying from more risky sources and that is not always a guarantee.
I believe you need to first learn to grow cannas and not be overly concerned about virus issues the first year. You may need to learn to identify potential diseased cultivars; how tall certain cultivars will grow to fit your needs; water requirements; how to amend your soil; over-wintering the cannas etc. If necessary you can discard any or all of the diseased cultivars and start with clean stock next season.
Cannas typically grow very well in full sun provided they have plenty of water and fertilizer, but like most things there is a learning curve and we all have differing growing conditions.
You may choose to limit your expense on rhizome selection and concentrate on your bed preparation etc. This would allow you to likely see both the good and bad. If you choose to make a larger investment in potentially virus free stock, do not purchase box store cultivars (they are not always virused).
I might recommend growing some of the seed strain Tropical Series seed but it may be a bit late in the season to start seed. Cannas grown from seed tend to produce virus free plants. Most seed generated seedlings will bloom the first year but depending on the source will not be clones of the seed parent.
There are a few suppliers that certainly attempt to supply virus free plants. You may want to check Plant Delight Nursery or Karchesky to name a couple.
Kent

Also, I've had luck getting Canna off Craig's LIst when I can see the growing plants. Looks healthy, I'll chance it. I plant away from others as much as possible to see how they do. If healthy for a year or two I then am OK with planting those closer together if needed. But I always try to keep groups separated.

Basically I'm trying to quarantine them as much as possible. No guarantee of course, but so far so good.

My theory is to try get Canna that were planted at a house many years ago, pre-virus, and have been isolated. It's the best I've been able to figure out. But it has limited my collection severely.