Congratulations on your decision to homeschool! Don't worry about extended family... they will see the proof in the pudding, so to speak, as your kids get older. It is difficult to give advice on which curriculum is best because it will differ greatly from one family to another, and even from one child to another. What one person tells you is wonderful, someone else will have an equally bad experience with it.
I homeschool my 5 & 7 year olds and we've been doing it since my oldest was 3. We use a variety of things rather than a "boxed" curriculum, which means you get all subjects from one supplier. For kindergarten we use Five in a Row ( www.fiveinarow.com ) which it a literature based program that covers social studies (including history & geography), science, language arts, art, and applied math. For math we like RightStart Math ( www.alabacus.com ). For phonics and reading instruction we like Reading Made Easy and Explode the Code.
The best place I've found to purchase curriculum is Rainbow Resource. They have the best prices and selection and shipping is free on orders over $150. You can request a catalog from them, but be prepared... it looks like a phonebook :). It is huge. Here is their website: www.rainbowresource.com .
I highly recommend getting involved with a homeschool group in your area. It will appease those family members who try to play the socialization card ;), and give your child an opportunity to make friends that homeschool so he can see that it's not a "weird" way to do school.
Good luck to you on your homeschooling journey!