We had our brooder up on a table as well. Our pups were curious but didnt bother them. We let our 80lb dog sniff the ducklings when they 1st arrived and they nibbled on his nose...he got totally freaked out and kept his distance ever since, lol.
The dogs still do great with the ducks in their run but we don't let them loose together just to be safe. I wish we could let everyone play together but I just don't trust my dogs enough.
We had a 3'x3' cardboard box for our first brooder, lined it with a heavy plastic tablecloth and used zip ties to hold the tablecloth in place at the top of the box. Worked great but not really intended for more than one use. Needed a cover over top as they grew as well.
Best of luck with your babies