So neat! Kids and animals sure do cook up some good photo ops! Post photos when you get a minute!
We vaccinate ours yearly with the 7 way vacc..but the vaccinations really depend on the area you live in and what the mare will be doing(shows, trail riding off property) For example, in my area of the country, Potomac Horse Fever doesnt occur, however, I vaccinate my show horses against it, as they might be at a show with a horse with the northeast that may be carrying it! Your vet will know best.
Oats are a great thing, however in older horses, watch to make sure they are able to chew them properly. I feed mine pellets, they are great, as with the older ones, Ive been able to wet them down and make a mush they can eat. I also fed my older horses beet pulp and alfalfa cubes..all soaked, to help them get their roughage and maintain weight.
Definantly have your vet take apeek at her teeth and get them floated if need be.
Here is a photo of my son and my mare, whom will be his mare, next year, jogging next to my husband at a cowhorse clinic we attended. She is 16 this year. gotta love them oldies!