We had a great time staying in Elwood. It's far enough away from St Kilda to be quiet (even though you're located on a main road), but still walkable to the St Kilda attractions and restaurants. The shopping strip on Ormond Road is only a short walk away and it had an awesome variety of food & shops.
The apartment had everything we needed for our family of four, and while our teenage son slept on the trundle bed to avoid sharing with his brother, he said it was comfortable & there were no fights over beds. The living room is spacious with 2 couches and we could all relax and watch tv in the rare moments we did that. While we didn't need to use it, having the full laundry in the apartment was appreciated and would have been super handy if we'd stayed any longer than five nights.
The weather was hot when we arrived so the short walk across the road to Elwood beach was great. While the car access was tight if you're not used to it, we fitted our station wagon in OK. Thanks Paul!