Hey there!
First things first, is that EVERYONE has an opinion. What tastes terrible to one person is absolutely stunning to someone else.
Good rule of thumb is that when first choosing juice, read and watch reviews. Some are more entertaining than others, but they will hopefully give you more insight into what may work best for you.
Second, try ordering from places which offer sample packs. In order to save yourself some money and time, take a moment to peruse the approved ECF vendor list, and see what people are saying.
Off the top of my head, some places which offer great sample packs are:
PureSmoker.com - USA Electronic Cigarettes & USA Made eLiquid!!!
BlueMist Vaping Supplies
JuicyVapor.com - Your one stop shop for all your vaping needs.
https://www.ttteliquids.com (also home of the crazy GOOSENECK)
There are plenty of others, thats just the tip of the iceberg.
Lastly, ask the particular vendors of they offer any sort of discount codes to save more money.
The juice in particular that I was using for the review (rou's toasted hazlenut tobacco) has VERY, VERY good vapor and flavor, and is offered as part of a TOBACCO SAMPLER PACK.
Vaperite
As far as coffee flavor is concerned, that's a tough one for me. Pure coffee flavor is just one that I don't particularly enjoy, so someone else might pop in to offer an answer.
Vaperite's Kona Cream and Prime Vapors Morning Blend were the exception to that rule.
http://www.primevapor.com/
I have to applaud you in trying to get your family to make the switch! I really hope it works out for you. Use the forums here as not only an informational source, but also for a support tool. We've all been there as new vapers, and will always be around to offer whatever advice and support we have.
Be well!