Hellobee Boards

They would be helpful, but you could manage without. LO is 16 months now and she will still eat sitting in our laps if we need too. We have a travel high chair too that is awesome that you could get away with or a booster? something like this:

We have this one that works great: http://www.target.com/p/chicco-hook-on-highchair-red/-/A-10019678?ref=tgt_adv_XSG10001&AFID=Google_PLA_df&LNM=%7C10019678&CPNG=Baby&kpid=10019678&LID=PA&ci_src=17588969&ci_sku=10019678&gclid=CIPfuYqIzLwCFctcMgodHj4ARw

We have a booster seat similar to this that we use when we travel. They're cheap enough that your MIL could get them for her house. And they'll last a few years until the boys are big enough to sit in the regular chairs.
http://www.amazon.com/Fisher-Price-Healthy-Care-Booster-Green/dp/B004C43JJ4/ref=sr_1_1?s=baby-products&ie=UTF8&qid=1392397522&sr=1-1&keywords=fisher+price+booster+seat