I just got LR for my 3.5 yo (and I have a 7.5 month-old as well).
3.5 yo already knows about 100 sight words.
Any tips for using LR with an older child?
TIA
Try a few of these, i use it with my 4 year old.
Make it part of your routine. Perhaps with morning tea or over breakfast.
If you decide to use both sessions try doing them with a gap between, eg day one part one then part two a week or so later. We just do each day lesson only once. He doesn’t like the repetition.
Get an iPad 
that was the best thing ever for LR!
Add phonics training soon. Use starfall.com, reading bear, readingeggs.com preschool prep DVDs or just teach your kids the sounds the letters make. Getting started on the phonics training is important in older kids.
Personalize some of the lessons to take out the baby bottles and playpen stuff if you think it’s irrelevant.
Act the fool with them, have fun.