You will love the Lucky Nugget, it's one of our favourites and your HB+ vouchers will cover the buffet cost.
Some of the restaurants mentioned above, California Grill, Cafe Mickey, Inventions will not be covered in full with your vouchers, although you could use them at face value and pay the extra.
The Chicago Steakhouse is very nice and does have a HB+ menu, so you'd be OK with that one. However, whether the Sunday Brunch there will accept your vouchers is dubious as a recent visitor reported that they would not accept them at face value, because of the inclusion of alcohol on the buffet.
Walt's also has a HB+ menu, but we've never eaten there so can't comment, although it has had good reviews.
Rendez vous des stars does look good and we're hoping to try it next time and will be fully covered by your HB+ vouchers in fact HB standard will cover it, Plaza Gardens, Agrabah Cafe and Annette's are also worth considering and standard vouchers would cover the cost of those too, again luck of the drawer but some visitors have reported using HB+ vouchers and having been given a voucher back in lieu of the cost difference.
Billy Bob's in the village is another that is covered by HB+ and again one we are hoping to visit in March.
Hope that helps.
Forgot to say as you're staying at SL I would choose to eat at the SL restaurant rather than at the Cheyenne's restaurant (Chuck Wagon Cafe), you'd be kind of downgrading if you did that
