We stayed in Carrbridge with our wee man in May who was 1 and a half at the time. We didn't eat in Aviemore often, but did go to the Bridge Inn and they were very good. They had high chairs and changing facilities and were happy to give us a small version of an adult meal as he couldn't eat anything from the children's menu.
I guess it depends how mobile your child is, but here's what we did:
Highland Wildlife Park
Funicular Railway
Steam Train (just went to see it arrive, didn't ride it)
Osprey Centre (probably no Osprey's in October though, but there's a nice loch walk there too)
Loch Morlich Beach
Landmark (he was a bit young for a lot of it, but really enjoyed the forest trails)
Walks round Carrbridge
Our chalets also had a swimming pool which I'm sure the McDonald in Aviemore does too. And there are some soft play places in the area if the weather is rubbish. We were lucky and didn't have to use these though.
There's loads of walks in the area. Not sure how many of them are buggy friendly, we used a baby carrier for walking.
We also managed to time nap time with a walk to the pub ;)