We use a sling to take DS to nursery. However occasionally he will be picked up by my mum who finds him too heavy for the sling. We would like to buy a pushchair for her to use - it will probably get 3 hours use a month. She doesn't want it taking up lots of room in her flat, and she would need to carry it to nursery so doesn't want it to be too heavy. Any suggestions (would be looking at buying second hand).