First off, does the app work on your Blackberry now?? The reason I ask is that your plan is supposed to give you access to specific social networking sites (facebook, etc) and BBM but you are not supposed to have regular internet access so the app shouldn't work. Great if it does!
So as far as US data is concerned, it doesn't look like Telus actually has US packages with a set amount of data. What they have is a $10 US Data add on that lowers your US data roaming rate from $3 per MB to $1 per MB. It says the savings start after 5 MB. Your usage you indicated above is less than 2MB (approx 1000KB per MB) because you are only doing BBM which doesn't use a lot of data. I'm assuming you have email as well which also uses very little data for emails that are TEXT only. If you have attachments or emails with pictures in them (like emails that stores send you) that would increase your data usage. So based on your regular usage you would only pay about $6 for your US usage for a whole month and the $10 add on would not be necessary. Now as far as the app is concerned I don't know how much data it uses so it might be a good idea to add that $10 US add on just in case. You may want to email the app developer and ask about approximate data usage so you have a better idea. The amount of data it uses shouldn't be alot as I imagine all the graphics for the app are stored on your BB and it should only be pulling small amounts of text data to update the wait times, etc. It also depends on how often it is requesting an update of data as the more times it requests the info the more data it is using.
As far as voice calling goes it is $1.45/minute and says you can call any destination. Again, they don't seem to have an add on with a specific number of minutes but instead have $5, $10 and $20 US Voice Pass that lowers your rate to $1, $0.50 and $0.25 respectively. So it depends on what you think your usage will be. You will definitely want to use BBM for "talking" to your hubby if separated as it will be much cheaper than a voice call.
Here is Telus' web page with all the info on the packages. Hope I helped!
http://www.telusmobility.com/en/ON/calling_services/usroamingpackages.shtml