1. providing you don't mind the cost, a second dock is a really sweet idea. I've been planning on getting a 2nd one eventually, myself.
2. I hardly ever go portable, but I have a case and think everyone should. Along that line of thought, get a screen protector...sooner than later. Hori makes a perfectly fine plastic one that has served me well, or there are gorilla glass types out there on the market as well.
3. joycon are not cheap. That said, if the money is not a problem, grab a second pair. Even if you don't have company that would necessitate a 2nd set, its nice to have an extra pair hanging on the docked Switch at full charge and at the ready. Get a Pro controller first and foremost, imo.
4. The sheer amount of quality games available for the Switch, whether at retail or in the e-shop, is staggering. If I may, I'd highly recommend Diablo3 as an early purchase. Its endless fun and the multiplayer aspect is great with friends and family.
5. Go with the largest sd card you can afford. I wouldn't suggest anything under 128g. Reasons being that there are so many great eshop titles to dl, and that there are many games that come physically that also require large downloads and they will eat up space rather quickly. ie. Mortal Kombat 11, Bayonetta 1/2 (if you buy them together 1 is a dl code), NBA2k, Doom/Wolfenstein2 etc, etc.
Switch has so much going for it right now. There's something for everyone. Enjoy and have fun with the family!
